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Surface and metal finishing field is going through continuous research and developments driven by REACH and process improvement demand. Some developments and contributions are on trivalent chromium, satin nickel, anodizing, aluminium conversion coatings, plating on aluminium, plating on plastic (PoP), and phosphating. A few proactive applicators focus on automation, process control, use of statistics, and bath purification.

Registration, Evaluation, Authorisation, and Restriction of Chemicals (REACH) had listed substances of lead, cadmium, chromium, cobalt, mercury, arsenic and solvents such as methanol and trichlorobenzene, and more.

 

Environmental concerns and market’s competitive spirit have motivated research and creativity. Let us overview the recent progresses with a few examples.

 

Trivalent Chromium

REACH, RoHS, and other environmental agencies across the globe had listed chromium trioxide (chromic acid) as a hazardous substance. Demand for decorative chromium in automotive sector (plating on plastic) and hard chromium in aerospace sector have forced the drive on trivalent chromium research for over several decades. Various formulations use chloride and sulfate salts of chromium to get the desired deposit properties. Industry had made much progress on advancing decorative chromium and modest improvements on hard chromium.

 

Anodizing

Boric acid and tartaric acids are replacing chromic acid in aluminum anodizing applications. Type 1 and type 2 anodizing using chromic acid and sulfuric acid contributed gigantically to the industry. Research and applications in boric and tartaric acids are making steady progress in the industry to replace hazardous chromic acid and extremely corrosive sulfuric acid.

 

Aluminum Conversion Coatings

Lanthanoids and actinoids had offered an interesting array of properties to replace hexavalent and trivalent chromium substances used in the conversion coatings. Other mineral and polymer-based formulations are in development and offered in the industry to meet vast conversion coatings demand of major sectors. Conventionally conversion coatings are an immersion process. Spray conversion coatings are finding unique value with some challenges.

 

Phosphating

Recent hard work is on to eliminate chromium and nickel from zinc phosphating and other phosphating applications. These newly developed formulations work at lower temperatures than the conventional processes.

 

REACH List Electroplating Changes

 

Automation


We need to move away from the traditional process improvement methods and be proactive in quality and cost reductions to achieve with ease the true electroplating capability.


Automation is the way to go!

 

Use automation to control the process parameters such as pH, metal content concentration, uniform current distribution (computational fluid dynamics (CFD)) and focus on creativity with human potential maximization aim.  The resultant distribution of the deposit depends on the choice of DC electroplating rectifiers above and beyond other parameters.

 

An Idea in Brief


We listed a few prominent thematic changes in our field. There are others like elimination of bioaccumulate perfluoro octane sulfonate (PFOS) and identification of boric acid alternatives on Watts nickel plating and acid chloride zinc plating applications.


 

While the listed developments are interesting and credible, we advise the process owner not be credulous when choosing a new formulation or a process. On some cases, the developments are significant and on some there are gaps in the meeting of required deposit physical characteristics. We recommend a process owner to acquaint with the salesman’s enthusiasm and a researcher’s curiosity, consequential in being carried by advantages and not projecting a balance of pros and cons!

 

Advint’s advisory services help clients on the best choice of processes, DC rectifiers and automation.

 

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Anodization is an electrolytic oxidation process where a substrate is anodic and the process forms a thick oxidized layer. We commonly refer to anodizing and chemical conversion coatings as light metal finishing. Aluminium, because of electromotive force (emf) series and emf potential, is a thermodynamically reactive metal and the most frequently anodized metal. We can anodize other metal alloys and there are several types and classes of anodization. In this short paper, let us look at the basics of anodization with specifics and a visual.

 

Anodized Metals

Other than aluminum, we can anodize magnesium, titanium, zinc and tantalum.

 

Applications

Anodization is a low cost and low maintenance application. Sectors such as aerospace, space, hardware and automotive industries, cookware, and mobile devices like cell phone use this process.

 

Types and Classes

Anodization possess good covering power, excellent adhesion, and is hard and scratch resistant. It finds applications on outdoor, architectural, and as a hard coat on engineering purposes. It is used to improve adhesion before painting. Aluminium and other refractory metals possess natural barrier layers, but anodized thickness layer is much thicker.

There are three types – 1, 2 and 3 and two classes – 1 and 2. The chemicals and thickness distinguish the type and class, and they are specific to applications.

We regularly use sulphuric acid on type 2 on both conventional and hard aluminum anodizing applications. Chromic acid, boric acid, and tartaric acid are used for Al anodization. Tartaric acid is one of the most environmentally friendly acids, whereas REACH and alike agencies identify chromic acid and boric acid (potential) as hazardous. Boric Sulfuric Acid Anodizing (BSAA) and Tartaric Sulphuric acid Anodising (TSA) are replacing chromic acid for the aforesaid cause. We can seal the anodized layers. Aluminum anodized resists chemicals between 4 and 8.5 pH, and they are good insulators.

Note: There are proprietary and non proprietary anodizing formulations available in the market.

 

Colours

Industry offers several colours of anodized layers like black, grey, pink gold, silver, copper tone, bronze, pewter, red, blue, clear and a few others. Dyes or pigments are used to colour the anodized layers before sealing and drying. Note, colouring and sealing are optional and on many applications are not preferred.

 

Processing Sequences

Cleaning, deoxidizing, etching, brightening, de-smutting, anodizing, colouring (dyes or pigments), sealing (DI water, organics and di-chromates) and drying.

 

Anodized Layer Thickness

The thickness of conventional anodizing layer range between 17 and 30 microns. Chromic acid anodizing and anodizing done on outdoor applications have much lesser thickness range - ~ 5µ. Thickness of hard aluminum anodized layer are ~ 4 mils.

 

Current Density

We can conduct conventional anodization at 12 ASF (~18 – 24V), between 10 and 60 minutes at 70ºF electrolyte temperature. We can conduct hard anodizing at > 25 V, and between 24 and 36 ASF.

 

Summary

This paper gives a simple outline of anodizing process for novices in the industry. Use the infographic to get quick information on the process and at a later month Advint will write an elaborate paper on this subject for forward-thinking users.

 

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Achieve a profound change in electroplating process control by asking inquisitive questions. Use emotional intelligence with curiosity, be intuitive, lay emphasis on quality over cost, and maximize human and automation potentials.  


 

Who does not want to advance their process performance? If we can improve the process without adding cost it is a windfall, correct? Maximizing automation of power supplies on electroplating, anodizing and electropolishing metal finishing applications is one such method. Automation helps process control. Above automation comes intuitive mind. Intuition is a derived from knowledge and experience. You ought to combine intuition with equipment capability. In this short paper we will review functions, capabilities and advantages of insulated gate bipolar transistor (IGBT) switch mode rectifier and silicon-controlled rectifier (SCR).

 

Intuition

Einstein nurtured his intuition from his experience working as a patent clerk while developing his theory of Special Relativity. His presence of mind and theoretical knowledge was instrumental in his brilliant work. Intuition and experience also played a significant role. Likewise, you can use your keen and meticulous observation skills, creativity, innovative mind, knowledge and experience to automate your plating and other metal finishing processes. Managing desires and possessing a non conforming mindset are nuts and bolts to achieve this trait.

Combine this attribute with knowledge in automation and on capabilities such as ampere hour reading and application of current during electrolysis for the finest results. Required capabilities for processes such as anodizing of aluminum, hexavalent or trivalent hard chrome plating, nickel and cadmium plating vary because of electrolytic conditions and electrode potentials.

 

Automation


Start with questions!

What are the automation opportunities?

Which option makes available the most benefit with less cost and complication?


 

Automating DC power supply is one of the best choices on an electrolytic process. An excellent choice on a rectifier allows the cathode to receive optimal current. Note, there is a difference between applied and received current. One can read previous articles in this page on current distribution, throwing and covering powers.

 

A rectifier with RS 485 and 4-20mA analog signal capability and ampere hour (AHR) meter can enable metering of process chemicals during electrolysis. Who doesn’t want consistent output quality? We must reduce variations within input variables to get the desired output quality. Among input variables there are parameters which vary by electrolysis and others vary primarily because of drag in and drag out of chemicals. It is pertinent to account for both types of variables. Rectifier, PLC and metering system can be programmed ingeniously to realize this aim.

 

With power supplies, begin by choosing between IGBT switch mode or SCR thyristor DC rectifiers. Ripple factor, unit weight, voltage and amperage accuracy are better with the IGBT rectifier. Ripple is a measure of purity of DC output of a rectifier. Many electrolytic processes, especially precious metals plating like gold and silver plating are sensitive to a higher ripple percentage. When a SCR rectifier is used at a lower amperage than the rated capacity of a rectifier, ripple is high. Whereas with IGBT rectifiers ripple factor is consistent and independent of DC output voltage. Green Power’s DSP digital control allows increased longevity with less maintenance of rectifier and comes with a very high accuracy. The DSP technology is proprietary to Green Power Co. Ltd. When compared with SCR thyristor rectifiers, IGBT power supplies possess higher efficiency and power saving capability.

 

In a nutshell, by choosing IGBT rectifier you choose better technology, save space and power, improve accuracy resolution and accuracy, and negate the effect of ripple factor. Use of RS485 MODBUS protocol can integrate with programmable logic controller (PLC) and control current, dosing systems and enable trickle current mode at the start of the process.

 

An Idea in Brief

 

 


Achieve a profound change in electroplating process control by asking inquisitive questions. Use emotional intelligence with curiosity, be intuitive, lay emphasis on quality over cost, and maximize human and automation potentials. 


We can automate hoist, process sequences, filtration and dosing systems, and rectifiers technologies with this outlook. A splendid choice of DC power supply is important. Both IGBT and SCR rectifiers offer unique advantages depending on the electrolytic process. Aluminum and hydrogen electrolysis, electrowinning and electroforming requirements differ from that of electroplating, anodizing and electropolishing. We recommend considering your process requirements with the capabilities of IGBT and SCR rectifiers.

On precious metals plating applications distinguish between applied and actual current. Due cognizance can affect the consistency of deposit thickness and the deposit characteristics. When sourcing a rectifier consider buying from reputed a manufacturer who conducts active research and continuously improve on their design and functionality.

 

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Managing time with a data-driven approach offers incredible value in process management and customer service on electroplating and anodizing applications. Analytical data, awareness of chemicals and deposit properties with a historical context add value to engineers and aspiring scientists in the metal finishing field.

 

Spot and quick tests offer incredible insights for the metal finishing processes. What is a spot test? Are these tests reliable?

 

High temperature oxidation resistance is a valuable elemental and deposit property. What does it mean? Which elements possess this property? We will review the value of this physical property.

 

Surface and metal finishing offer a variety of options such as plating, anodizing, coloring of metals and electropolishing. Plating on several substrates such as plastic, steel, stainless steel, Invar, Kovar, nickel, aluminum, and titanium alloys are common. Elements like gold, silver, nickel, chromium, zinc and cadmium are plated. We choose the deposit based on consideration for cost, corrosion resistance and tribology properties.

 

Other than plating, we can electropolish and anodize metals such as stainless alloys. Applicators anodize on aluminum, magnesium, titanium, niobium, tantalum, etc.

 

Anodising is an electrolytic process in which we make an Al alloy anodic with a metal cathode on an acidic electrolyte. There are three classes of coating. We anodize with and without sealing.

 

This short paper explains which element to choose as deposit or substrate. It lists spot and quick tests available in the market. Review brightener chemistry and history. Discuss inhibitors, chemicals used for coloring metals and chromium conversion coatings.

 

Spot Tests

Several wet and instrumental analyses methods are used to conduct qualitative and quantitative analysis of elements. The advantage of these methods are accuracy and data reliability. But these test methods are time consuming and some are expensive. When you need a quick feedback, consider conducting spot tests on deposits and effluents. The sensitivity of spot test reaction can be at ppm levels. Elements such as aluminum, stannous tin, gold, silver, iron, nickel, palladium, lead, zinc, cadmium, chromium and copper can be tested. Many of these tests can take less than 5 minutes.

We can detect heavy metals, hexavalent ions and cyanide content in the effluent. You can distinguish between cadmium or zinc plating deposits using spot tests.

 

Here is a list of some organic chemicals used for spot tests:


Diphenyl carbazone

Dimethyl glyoxime

Tri-ammonium aurine-tricarboxylate

Nitro-bruciquinone hydrate

p-Dimethylamino benzylidene rhodamine

diphenyl thiocarbozone

sym-Diphenyl-carbazide

(1-2-Hydroxy-5-sulpho-phenyl)-3 phenyl-5-(2-carboxy-phenyl)-formzan) sodium salt

1-(2-Pydridyl-azo)-2-naphthol


Refer to Chem Spider for further information on any chemicals.

 

For further information on spot tests, read the book - Analysis of Metal Finishing Effluents and Effluent Treatment Solutions. This is a book written by Duncan MacArthur, Fred Stevens, and G. W. Fischer.

 

Chemicals

Did you know tobacco and licorice were one of the earlier brighteners used? Several decades ago, or even a century back, the use of brighteners or additives were very limited. Even the awareness of organic brightener science did not exit. Like many inventions, use of organic chemicals as a brightener was an accident. Tobacco was one of earlier recorded chemical used as additive. More than a century ago a plating operator who had the habit of chewing tobacco drooled the juice onto a plating solution during electroplating. Later noticed that a plated lot had a brighter appearance. Further investigation revealed the brightness influence of tobacco on plating deposit.

People used licorice during earlier days. It had a presence in the industry for some time and even now to an extent. Licorice extract is a carbohydrate and its chemical name is glycyrrhizin. They used it as an additive.

 

The additive was prepared by weighing a known quantity of licorice root and steep in a boiling water until colour saturation occurred. For 100 L plating solution, 100 grams of root was steeped in 0.5 L of boiling water.

Pickling and acid activation are a very common process at a steel mill, metal foundry, and a metal finishing processing plant. Conditional on activation and deposition bonding requirements, a substrate such as copper alloys or steel alloys would require activation under strongly acidic conditions. Use of strong acids such as hydrochloric acid, sulfuric acid and hydrofluoric acid can etch the substrates.

 

We commonly use sodium fluoride as an inhibitor. On picking applications, industry used antimony trioxide as an inhibitor.

 

Copper alloys such as brass tarnish in the presence of oxygen from atmosphere. Brass plated deposit do the same. An organic coating can prevent tarnish. Benzotriazole coating forms a thin layer in an immersion process, and the layer protects copper alloys from tarnish.

 

Brass plating is an alloy deposition process. The electromotive force potential of copper and zinc makes cyanide brass plating one of the most complex electrolytic processes. Attainment of a consistent and durable colour is tricky. Proper use of current density with an excellent choice of rectifier (IGBT or SCR) with an organic coating ensures great cosmetic appeal with durability.

We can also colour brass. One such colour is blue. An immersion process at high temperature in the presence of sodium sulphite and lead acetate colours brass substrates. Other than brass, we can colour stainless steel alloys using dichromate salts.

 

Yellow chromate on zinc deposit is one of the popular choices. We recognize the yellow chromate for brilliance of colour and corrosion protection. There is a subtle colour difference different between hexavalent and trivalent chromates. Chromates sometimes leaves iridescent finish. A protective coating similar to benzotriazole layer reduces iridescent streaks.  One can get a reddish tone on the yellow chromate formulation. Use of a sulfate ions and nitric acid offers a reddish yellow chromate finish.

 

Occasionally people refer to chromate or chromium plating as chroming. Chroming is a colloquial speech term and we prefer you avoid using informal terms to avoid confusion and for use of clear language communication. Hexavalent Cr and (cyanide) cadmium is listed by Registration Evaluation Authorization and Restriction of Chemicals (REACH). We now replace cadmium plating with zinc / nickel alloy. Sacrificial protection of cadmium under saline conditions are inimitable.

 

Deposit Properties

Observing electromotive force series of elements and their potentials (negative or positive / active or noble) suggests evidences on fascinating deposit, material or electrolyte properties. We are referring to properties such as high temperature oxidation resistance and conductivity.


Pilling and Bedworth conducted a seminal work on high temperature oxidation.


Chromium, tantalum, zirconium and gold possess exceptional high temperature oxidation resistance properties. What is high temperature oxidation resistance?


The volume of oxide is greater or lesser than the parent metal, it produces or cannot produce an effective protective property.


What does a reference to protective property mean? It refers to the formation of an oxide layer, such as tantalum oxide, chromium oxide and zirconium oxide on the metal or the deposit. The refractory metals offer oxidation resistance up to ~ 600ºF. Oxidation and healing property are the principal reason hexavalent hard chromium plated components had gained wide popularity. Many applications of aerospace and automotive industries require components to posses tribological properties at a higher temperature. Wear, lubrication, and friction are such examples. The oxides can re-form and withstand high temperatures during these mechanical transformations. Tantalum, zirconium, niobium, and chromium metals are a few among the best to possess such a property. Other than oxidation properties, these elements are susceptible to corrosion resistance from acids, alkalis, organic media and other reagents. We measure high temperature oxidation in ratio and Pilling - Bedworth (PB) ratio of corrosion resistant metals range between 0 and 4. Higher the number better the corrosion resistance. PB ratio is the ratio of the metal oxide volume divided by the metal volume. Chromium PB ratio is 2. All chromium electroplating deposits do not have the same corrosion resistance properties. Corrosion resistance of decorative Cr plating is because of nickel undercoat. Most hard chromium deposit do not have any corrosion resistance. However, a few formulations containing fluoride ions in the electrolyte possess high corrosion resistance. Some hard-hexavalent Cr deposits pass 500 hours of neutral salt spray test (NSST). We mainly attribute the variations to formulation, processing, and process control.

 

Other than refractory metals, precious metals such as gold plating deposit possess high temperature oxidation resistance. Industry uses gold plated components on space applications because of high temperature oxidation resistance, conductivity, high surface stability, high resistance to tarnish, and chemical corrosion. Both trivalent and monovalent salts are used to deposit gold from electrolytes. Precious metals like gold, silver and palladium can be plated on several substrates such as stainless steel, Kovar, Inconel, magnesium, aluminum and titanium alloys efficaciously.

 

Besides lightweight, the stubborn oxide layer makes aluminum and titanium alloys indispensable in our daily lives.

 

Previous paragraph mentioned about the conductivity of deposit. What about electrolyte conductivity? Change of ion activities with concentration affects electrolyte conductivity. Understanding interionic attraction theory of electrolytes are essential to improve conductivity.

 

Value

Whether you are an engineer or a research scientist, understanding element and deposit properties, electrolyte capabilities and limitations, and vitality of unique chemicals are important. A process design engineer with a good understanding on these characteristics can design products with superior corrosion and tribological properties. The matters covered in this paper such as high temperature oxidation resistance can help a designer identify suitable metal as substrate and a deposit.

 

We identify some chemicals listed in this paper as hazardous or carcinogen per Registration Evaluation Authorization and Restriction of Chemicals (REACH). REACH is a European Union regulation. You can also find additional information on carcinogens by visiting the website of National Institute of Environmental Health Sciences (NIEHS) under the National Toxicology Program (NTP). Observing regulatory compliance and identifying risk mitigation plan will drive an organization’s governance.

 

REACH, quality demand, and customer requirement will call for a transformed focus on a few facets such as colouring of metals, plating solution additives, chromium conversion coating and anodizing. An ardent electroplating specialist must consider all the services, test methods and fundamental concepts.  

A leader must prepare electroplating companies to manage complex processes. An agile metal finishing organization aiming to survive even under adverse conditions shall be data driven, ensure speed of business is appreciable, work faster, and inculcate easy-to-use test methods. We know many that plating companies who are not data driven do not grow or adapt to developing changes.

 

Spot testing of effluent, electrolyte or deposit is an under used method, and will help gather data with speed and ease. Other quick tests like pH measurement, specific gravity, litmus, refractometer, and profilometer are all easy and inexpensive. This do not mean volumetric and instrumental analysis offer less value. Both methods are vital for many electroplating operations. The choice depends on their technical ability, product testing requirements and financial capability. The examples of these instruments are atomic absorption spectroscopy, scanning electron microscopy, induced couple plasma (ICP), x-ray diffraction, x-ray fluorescence and electron microprobe analysis. We use these units for elemental analysis at lower concentration with a top-level accuracy. XRD and EPMA can detect light elements such as lithium, oxygen and carbon with an outstanding repeatability and reproducibility.  

We deliberated chemicals, methods, properties, and data driven approach. Cognizance of these matters without a long-term analysis and reaction plan is not noteworthy!  Consider use of run chart, control chart and Process Development and Control (PDC) tools with a visual dashboard.

Readers can find a value on other short papers written on this page previously. Please read articles on electrode potential, IGBT and SCR power supplies, current distribution, throwing power, periodic table, Time Change Management (TCM), Process Development & Control (PDC) tools, and communication. A complex electrolysis process requires a multidimensional approach on disciplines such as science, mathematics, technology and management. There are many vital aspects involved in this field such as automation, process control, business development methodologies, and so on. Fundamentals, laws, equations, and concepts govern electrolysis. Though not needed on a day-to-day basis, these are important to be aware and apply. Discipline, observation, data, patterns, and behaviors are critical for one to succeed at a higher level. Though there will be a scientific explanation for all outputs, one needs to treat the work as art! This is imperative because of our limitations – time and knowledge. Hence, at Advint we offer on guidance on subjects related to laboratory practices, equipment engineering, automation, productivity, lean, statistical process control (SPC) tools, and management. Advint’s virtual Electroplating Training explains all these subjects comprehensively. 

 

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Surface profile of the substrate, specifically surface activity and its receptivity to accept electroplating deposit spontaneously determines the morphology.


A deposit with good morphology will possess an adherent deposit. There is a myth and inadequate science work related to surface profile and adhesion. A few sectors do well with improving surface activity and a sector is vulnerable. This short paper intends to shine light, dissipate a myth and suggest improvements with supporting information.

 

Cleaning & Activation

It is a normal practice to blast a metal surface to improve cleanliness. This approach predates the 60s, when cleaner science had made minimal progress. Over the years proprietary plating supply houses like Atotech, MacDermid Enthone and Coventya had conducted extensive research and offer a wide array of cleaning products. We released a short paper explaining the importance of cleaning on April 1, 2019.

 

In the absence of an effective cleaning process, blasting the surface is pertinent. It is an important treatment method on applications where we require higher Ra values or unique aesthetic appeal. Rather, if one blasts a surface merely to improve adhesion, then it is time to debunk the myth! Now, I’ll back up the purpose with facts and information.

 

To get an adherent deposit the metal surface must be clean, active and receive nucleation (form a unimolecular layer) within the first 10 or 20 seconds regardless of the current distribution pattern. A spontaneous and uniform deposit formation is important. The critical nucleation time varies between substrates and the deposit element’s electrode potential.


A truly active surface allows effective nucleation.


A poor nucleation layer will disrupt crystal growth and cause re-nucleation of the crystals. This disruption leads to deposit non-coherence and inconsistency in physical characteristics, resulting in premature product failure. Impregnated blasted media is very difficult to remove completely from the surface and in most cases leaves a residue, hinders nucleation or continuity and uniformity of the deposit. An electropolished surface address this concern and enables epitaxial or pseudomorphic growth when and where applicable. This surface possess very low Ra values, are active and free from foreign materials. If it drives you to get the most adherent deposit, electropolished surface is one of the best means to achieve this endeavor.

 

electropolishing electroplating surface profile

 

Surface Profile & Adhesion


A truly active metal surface can form a thick intermetallic layer and develop a single domain deposit morphology (columnar structure) through the process. A single domain columnar structure deposit will possess a distinct grain boundary.


 

This mechanism is not independent of process control. The author of this paper had conducted extensive research over a decade on this matter, and so did a few other scientists from our society during the 80s and till now. A deposit with an intermetallic layer forms the most adherent deposit. In order for a non-electropolished surface to form an intermetallic layer, it must possess an active surface. We know that an electropolished surface possess lower Ra value, but we require more controlled studies to validate the relationship between the surface profile and adhesion. On this subject, good surface profile implies a clean, smooth and active surface.

 

Morphology & Physical Characteristics

Most adherent deposits possess good morphology. A deposit with an intermetallic layer and undisrupted columnar structure will have greater than 20% improvement in physical characteristics such as hardness, tribology, and corrosion resistance properties. 

 

Summary

Blasting is a valuable pretreatment method, but an ambitious applicant must recognize that residue left on the surface affects the deposit characteristics and it is not a certain choice in pursuit of an adherent deposit. Electropolishing is not practical on many applications. Exceptional cleaning and activation are viable and important.

 


Accomplishing an intermetallic layer on all applications is an unreasonable expectation, but a clairvoyance can set that as an aim. This aim is akin to lean’s one-piece flow and six-sigma.


In short, be mindful of the relationship between activation, morphology and physical characteristics.

 

Notes:

Material scientists and electrochemists now and then use different terminologies when referring to the same concept. Some terms used in this paper are no exception.


I used material scientist as a substitute for metallurgist. The global technical community replaced the term metallurgy with physical characteristics in 2010.

 

You are welcome to post a comment or email with questions to adviser@theadvint.com if a concept is abstruse.

 

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This paper is neither about politics nor about the ongoing pandemic. It is about the Hawthorne effect, the obvious but not so obvious effects, and the necessity.

 

As the title suggests the USA economic performance, DOW index gains and President Trump’s drive to stimulate the economy over the past three years is akin to the Hawthorne effect.

 

Electroplating, anodizing, electro-polishing and complex processes such as plating on plastics require leadership drive to advance operations and engineering performance, and sustain on the growth.

 


An exemplary leader sets the expectation, creates necessity, delegates responsibility and confirms accountability without micromanaging the trivial effects.


We can set a clear expectation on variables such as electrochemical variables, process yield, product flow, inventory management, employee and executive management engagement.

 

Hawthorne Effect

The Hawthorne effect is the improvement detected because of a noticeable observation of the process. In reality, it does not confine the effect to a process, rather it encompasses to an employee performance. In both cases, it is a top-down approach, but ends with a continuous observation from all levels. When a leader sets the expectation, consistently follows up, align the goals with his or her actions, and support their team to succeed, the team would achieve operational excellence in the long term. Observation and commitment to improvement must include all critical key performance indicators (KPI’s).

 

Obvious but not so Obvious

In retrospection, every challenge we overcame and the opportunities for improvement would become obvious to us. But this is late, as by this time we would have non-conformances, cost infliction and customer dissatisfactions. It is prudent to detect the obvious challenges and opportunities in real time. Earlier the opportunities were present, but hidden. We miss as it is not obvious!

 

If I did not communicate, think about the current COVID-19 pandemic. The issue originated in December 2019 and peaked in China during mid-February 2020. If the issue was apparent to global leaders and commoners around January, would the consequences be the same?


Revealing the hidden challenges in real time is the heart of your effort in improving effectiveness.


 

How to expose these challenges? What prevents us from reading between the lines? The answer is not simple. This would be contingent on the leader’s emotional intelligence, knowledge of the subject and availability of visual data and information on real time.

 

Electroplating anodizing process line

 

Yield Shadows Necessity

We can achieve metal finishing processes and business effectiveness by focusing first on necessity. One must focus on the necessity to perform, collaborate, and on satisfaction (employee and customer). Yield will shadow the necessity–big or small; it is for you to choose! Clear responsibility and unambiguous accountability are the means to achieve necessity.

 

An Idea in Brief

Electroplating and other metal finishing processes are complex, as we all know. Market and customers are demanding. Contingencies like the COVID-19 pandemic will subject job shops and captive platers to hardship.


At these and regular times, being conscientious of the process variables, exposing the hidden opportunities on real time, and starting with a focus on necessity are three important steps to achieve effectiveness in the manufacturing operation.


 

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On a metal finishing processing line, among many design factors, choosing a rectifier with correct technical specifications and capacity based on production capability is very important. Predicting a production capability on most lines on a long term, particularly for a job shop is tough.


However, a correct choice on the capacity of a rectifier and on technical specifications will turn errors to account on a process performance.


 

Besides specifications, cost of a rectifier, power consumption and automation capability are significant considerations for a meticulous procurer.

 

IGBT and SCR Rectifiers

There are two types of rectifiers - Insulated gate bipolar transistor (IGBT) switch mode and silicon-controlled rectifier (SCR) thyristor. SCR rectifiers are suitable for high voltage and high ampere applications, but IGBT rectifiers possess higher efficiency, greater power factor, higher resolution, faster response time and constant ripple. Ripple matters in a plating application with an SCR rectifier and on precious metals plating.

 

DC rectifier Power supply

 

Using a rectifier at the lower end of its rated capacity affects the ripple factor. On some applications there will be a negative influence on current distribution and throwing power of the deposit. A few deposits are tolerant than others. Precious and other transition elements differ in this attribute. Much of them are because of price. At a sub optimal capacity combined with a poor specification, a rectifier can yield a deposit with defective morphology compromising adhesion and the physical characteristics.

 

Note: Ripple is not the only cause a compromise can occur on the morphology of a deposit. Among many other variables, Helmholtz electrical double layer effect has a substantial effect on the morphology with the continuity of the deposit.

 

Other than ripple, there are cost impacts. A client of Advint, about 3 years back, purchased a 25,000 amperes rectifier. On most loads they had applied ~ 10,000 amps and seldom they applied 15,000 amperes. And the applicator does not foresee applying 20, 000 amperes within the next few years. The tank volume and the rack capability do not support the calculation. In hindsight, the applicator could have saved by considering a lower ampere rectifier (written with the Applicator’s consent).

 

On high ampere applications, power consumption is an important factor. When the distance between shunt and electrode terminals are higher, power consumption (resistivity) and cost is high.

 

Automation and Digital Control

On automatic applications, metal finishing industry uses human-machine interface (HMI) and programmable logic controller (PLC) capabilities for a long time. These interfaces are useful for current density calculations, plating time, ampere hour (AHR) control and chemical metering or dosing system, though the options are limitless. All chemical variables in a process are not consumed by electrolysis, rather a few follows adsorption mechanism. On these cases the use of PLC’s ladder logic, count down or count up timer will help. The MODBUS RS 485 serial communication protocol is the standard now to monitor and control the system. When a rectifier possesses higher end capability, and we maximize utilization even on a manual application, an applicator can see an advantage in labour cost and process control.

 

Ensuring we do not overload a rectifier, can extend the life of the rectifier. A periodic preventative maintenance program will support the same cause.

 

A Brief Idea


This short paper has brought to light the advantages of IGBT rectifier and the use of HMI/PLC interfaces with MODBUS RS 485 serial communication protocol.


Due diligence on specifications and productivity planning reduces fixed and marginal costs, improves the quality and consistency of the coating (electroplating deposit and anodized layer) processes.

 

 

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This is the second year of short papers release. Last year, Advint released papers on cyanide ions, properties and behaviours of anions, trends within the groups and periods of the periodic table, electroless Ni and current distribution (primary and secondary), quality and management. A year ago, I wrote about electrode potential and electromotive force (emf). As an example, nickel and gold possess distinct electrode potentials, and so are their deposition mechanisms.

 

Reel-to-Reel Plating

Electronic industry regularly uses gold, tin, palladium, palladium/nickel and copper on a continuous reel-to-reel plating application. Similar to gold, tin and indium possess comparable properties and advantages. Tin, silver, copper, indium, and gold all possess good conductive property. Indium, a precious metal, we primarily use as an alloying material in plating applications, though they use it as a deposit by itself (without alloying element).

 

Palladium and nickel are neighbors in the periodic table. We consider palladium to be a precious metal and it also possess properties comparable with nickel. It is broadly used in electronics and jewelry industries. On many applications, palladium or palladium/nickel acts as a good undercoat (an intermediate layer). Palladium/nickel deposit is recognized for its cosmetics, and wear and corrosion resistance properties. The ratio of palladium and nickel in the deposit varies between 80 and 20 to 95 and 5, respectively. Palladium also gained prominence because of nickel release and nickel allergic properties. Upsurge in dominance of palladium is apparent when we look at the price of the metal in the market (today’s value - ~ USD 2213 per troy ounce).

 

hard chrome plating

 

Plating on Plastics (PoP)

The demand for nickel on other hand is rapidly growing in the automotive industry, particularly in plating on plastics applications. The wide acceptability of nickel is because of its refractory properties, though it does not belong to elements of the refractory group (periodic table). Nickel release and its allergic properties are an issue in certain demographics and on applications such as eyeglass frame, earring, necklace, ring, bracelet.

 

On PoP applications, plastic substrate preparation using a colloidal catalyst is one of the most important steps. On acrylonitrile butadiene styrene (ABS) plastics, it follows preparation of the substrate with electrolytic copper, nickel and chromium deposits. Among Ni use, electroless Ni is gaining wider acceptance in recent decades. The industry also now replaces hexavalent Cr with trivalent chromium.

 

Electrode potentials are distinct between hexavalent and trivalent Cr plating applications. The trend is the same on other metals such as Ni, Au, Sn, In, Cu and Pd. The properties are distinct not only because of electrode potentials but also because of transportation of ions and ionic mobility. Similar to chromium, ionic mobility of electrolytes of electro-polishing and anodizing are also less. This is one reason these require a very high DC voltage from the rectifier during processing. Note: A paper on rectifier is coming soon.

 

Summary

Different metals deposition mechanisms vary because of their electrode potentials and other properties like ionic mobility and concentration of metal ions.


Among many elements of reel-to-reel plating and PoP applications reviewed in this paper, Pd is used on both applications, and has gained significant recognition in the recent decades.


The recognition goes beyond plating applications.

 

 

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Creating a surplus is an implicit ambition of our real time contribution. The effectiveness of our drive makes a positive difference and offers maximum customer value proposition (CVP).

 

How do other sectors and manufacturing industries innovate and manage the fundamental concept of creating a surplus?

 
What surpluses mean?

Surplus is receiving more money than paying.


 

plating industry

 

Surplus is an economic concept. This paper aims to strive beyond economic and financial prudence to improve and sustain on surplus. A profound strategy using traits like conformance, time management and decision making will help transition to a new approach. 

 

We all have a procedure, a standard and a key performance indicator (KPI) to follow and observe. There is conformance and non-conformance. We are not referring to product conformances, rather we are discussing conformance trait of our mind. We use business improvement methodologies like ISO, lean and total quality management (TQM). Use or somewhat overlooking to use this trait properly is what defines as a route to the maximation of surplus.

 

Use of ISO standards and concepts in the beginning of growth stage is valuable. The standards used today must not hinder our ability to change tomorrow. A non-conforming mindset, swift decision making and managing time followed up with the revised adherence to ISO principles are one of the simplest means to realize CVP quickly.

 

What is the value of time?

Carl Sandburg wrote, “Time is the coin of your life. It is the only coin you have, and only you can determine how it will be spent. Be careful lest you let other people spend it for you.”


 

There is a plethora of lean tools. The uniqueness of lean is not in its tools but in its emphasis of culture. Adaptability and change combined with decision making is the most important means to the path of surplus.

 

Most use TQM on their work applications. On electroplating and plating on plastics applications, mere use of statistical tools is not sufficient. We recommend starting with 6 process development and control (PDC) tools and train ourselves to see the not so easily seen variations.

 

A New Approach in Brief:

 

Technology and finance sectors use information technology (IT) to boost the growth and analyze intricate information which human eye and mind rarely recognize. Sectors within manufacturing industry often use innovation to stay ahead of time. Use of standard and tools like ISO, lean and TQM produce fair CVP. To maximize CVP and create excess surplus, how we use the standard and tools matter the most. Ability to change, managing time and prompt decision making in real time will enable our organizations’ evolution to a new approach.

 

  1. Leaders in technology and finance sectors who are adept at decision making do keep in touch with data and information on real time. Knowing the surroundings and being focused is a basis to be decisive and disruptive.
  2. The leaders do not consider past performance or guide as a benchmark or a standard, respectively. We recommend leaders to examine and revise the standards and opportunities endlessly.
  3. As Sandburg aptly put it, time is precious. Masters control the time and destiny.

We advise the electroplating management team to focus on surplus to coin money without difficulty.


 

Often you must consider originating a new approach with cognizance of conformance, decision and time.

 

Whatever that approach might mean to you and how and in what way it might be new, I’ll leave it in your capable hands!

 

 

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Cyanide based electrolytes of silver and copper deposits possess excellent throwing power property.


None of the nickel or chromium electroplating electrolytes contain cyanide ions.


The paper discusses the polarization, coordination chemistry, and thermodynamic reasons for these phenomena.


Did you ever think about why nickel does not possess a simple cyanide-based plating electrolyte? Why can’t we electrolyze a nickel cyanide salt [Ni (CN2)] to get a deposit? Won’t a cyanide nickel electrolyte with a good active polarization and throwing power property be of use?

 

We will deliberate the evidences of asking these questions.

 

Cyanide based electrolytes such as silver and copper deposits possess excellent throwing power. Copper possesses good leveling characteristics, while nickel without organic molecules has negative throwing power. Bright nickel with class 1 and 2 brighteners can get a uniform deposit on the cathode, but it is not comparable with copper.

 

Coordination chemistry plays an important role in electrolysis. It is important to distinguish thermodynamic parameters such as stable and unstable, and kinetic parameters such as inert and labile. These terms refer to stability. Nickel and chromium cyanide complexes like [Ni (CN)4]2- and [Cr (CN)6]3- are (extremely) thermodynamically stable. Unlike kinetically inert compounds, thermodynamically stable coordination compounds become very difficult to break a bond or ligand during electrolysis.

 

cyanide copper plating

 

Silver and copper cyanide baths possess good throwing power because of the presence of simple cyanides like sodium or potassium cyanide. Cyanide ions during electrolysis effects total polarization. The concentration polarization increases at the cathode interface because electrolysis liberates cyanide ions. The concentration polarization and cathode current efficiency work in tandem and distribute electrodeposition based on primary and secondary current distributions factors. This behavior is a part of tertiary current distribution phenomenon.

 

Ni and Cr are not incomparable with their limitations. Platinum and gold have unique advantages and restrictions. Like Cu and Ag, brass plating containing cyanide ions produce beautiful deposit colour. In aqueous electrolysis Cu, Zn, Ag & Cd deposits differ from Ti, Zr, V & Nb. These points emphasize distinct properties and limitations of elements, chemicals and media (aqueous or ionic).

 

Purpose

The short paper does not offer a solution or recommend an alternate method. It explains the fundamental benefits of cyanide ions and distinguishes unique elements of the periodic table like Ni and generates an awareness on their chemical properties.

 

Understanding the characteristics of an element, position in the periodic table, and their chemical properties are important to research scientists and advanced engineers.

 

If you are a scientist formulating a bath recipe or a forward-thinking engineer choosing a process to meet deposit characteristics’ fundamental concepts, advantages and limitations are important to understand. This learning will take full advantage of the prospect or prevent an issue in the long-term.

 

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Venkat Raja
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September 1, 2020
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