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Is surface profile of the substrate pertinent for an effective adhesion of the electrodeposit? Does it only improve the aesthetics or also influence the functional properties? What are the options? Do treatment methods vary with substrates?

 

This short paper answers these questions and offers a synopsis of those processes. The processes are blasting, mechanical polishing, vibratory bowl movement, bright dip, chemical polishing, and electropolishing. 

 

Blasting

Industry uses abrasive or sand and glass bead blasting methods to clean and change the surface profile of the substrates before plating. Silica, aluminum oxide, and glass beads are the often-used media at various grit sizes. Machines and manual booths (closed) are used to execute these methods. This is an age-old technique. It is a simple process, but leaves impregnated particles on the surface and, if not properly removed, might affect the next processes (cleaning and plating).

 

Polishing

On mechanical polishing and similar category falls polishing, buffing, lapping, and grinding. Unlike buffing, polishing removes the metal surface. Lapping and grinding change the surface significantly. Industry uses muslin, canvas, leather, etc. as polishing wheel materials. Muslin is most extensively used as a buffing wheel. These mechanical processes are used to improve the aesthetic appeal of the substrates. As further pre-cleaning is involved before polishing, the polished and buffed substrates reduce the load on plating line’s pretreatment processes.

 

Vibratory Bowl Movement

Deburring and improving Ra value of metals are the primary applications of the vibratory bowl movement method. We can use this method on several metals and substrates (before plating) like copper and beryllium alloys, stainless steel alloys, low and high carbon steel alloys, nickel and titanium alloys, and several others. Size and shape of the substrates, media, chemicals used during the bowl movement, speed of the movement and time control the resultant finish. Unlike mechanical polishing and blasting, the process doesn’t leave residues on the substrates.  

 

Bright Dip

As the name implies, this process improves the brightness of the substrate. It improves the surface profile and helps aid oxide layer removal. This is an immersion process mostly using an acidic solution for 5 seconds to 5 minutes. Commonly used substrates are ferrous, copper, beryllium, aluminum, stainless steel, nickel, and Monel alloys. Zirconium, titanium and silver metals can also be bright dipped. These processes cost less, and the solution life is short.

 

Chemical Polishing

Chemical polishing process is like bright dip, but removes more substrate material. Many copper alloys and a few ferrous alloys can be chemically polished. Some chemicals are toxic and need good air ventilation for a friendly environment, health and safety practices.

 

Electropolishing

Electropolishing is an anodic process. Electrolysis selectively removes micro – peaks of the substrate metal. This process offers superior passivation and corrosion resistance properties on 300 and 400 series stainless steel alloys. The passivation properties got from electropolishing are better than nitric acid and citric acid passivation processes. Common metals electropolished are 300 and 400 series stainless alloys. Other alloys are Al, Cu, Monel, nickel, silver, zinc, tin, Co, Ti, and low and high carbon alloys.

 

Electroplating Surface Profile

Summary

These methods can alter the surface profile of the substrate metal before electroplating. Cost, chemical hazard, and awareness distinguish the choice and application of these methods. Each method has advantages and disadvantages.


Blasting is the easiest. Vibratory bowl movement and electropolishing methods offer the best aesthetics and functional properties after the deposition process.


 

We can enhance the deposit brightness, leveling characteristic, adhesion and surface profile Ra values using any of these processes.

 

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In the changing times as now, expectations on quality and services differ. A plating company is no exception. The sector is not at the forefront. When expectations grow, re-alignment of vital trademarks of an electroplating organization must change. The change must happen with a focus on data science, creativity, finance and behavioral science over a long period. Except data science, none of these are new. But the application, the discipline and methods have adapted. When a plating organization defines and uses these four trademarks, they become ‘agile’. This short paper explains the characteristics of these trademarks and spills the beans on its returns.

 

Agile Electroplating

Data Science

Surface and metal finishing sector are on the precipice of embracing data science. Many large automated electroplating plants have unintegrated big data. Several variables and analyst’s processing abilities limit conventional statistical methods like control charts and design of experiments.

 

A proper use of statistics and inclusion of a software program with algorithm enables big data to be integrated on many variables. Use of data science enables predictive analytics. The common tools are error trend seasonality (ETS) and auto-regressive integrated moving average (ARIMA).

 

So, what are the returns? Is data science better than simple statistical tools? The answer lies in the scale and the ease with which we can do a complex study with big data within a short period. These analyses can detect variations in hoist performance, rectifier applications, and laboratory data. Data collection and analysis in real time will make sure predictability and compel corrective actions of the processes and equipment.

 

Finance

Finance plays an integral role in daily activities and on long-term capital projects. Proper use of marginal cost concept on daily activities and return on investment (ROI) or net present value (NPV) method on capital projects is pertinent. A dynamic team deals changes with apt financial methods, and it yields pure profit and opportunity cost value. A well-structured bill of materials (BOM) and use of data science will show non-conformances in a process at an early stage. This will help management react to changes. A balanced usage of financial and or accounting practices with statistics and data science will produce optimal quality results.

 

Creativity

Creativity inspires innovation. Develop necessity and enable trust to seed creativity.


In the absence of creativity and motivation, a team member can’t bring disciplines like data science and financial management to fruition.


Innovation on input and output variables, automation and DC rectifier 4-20 mA controls can refine and alter the process performance. Many variables and big data demand software programs, as manual analysis become overwhelming and overlooked. We can be creative and innovative on data, technology, behavior, and science.

 

Behavioral Science

Many of us engage in matters we liked, we have studied, and we corroborated. There is a valid reason for this conduct. Many times, we are right. Sometimes we sustain on our validated thoughts. When challenged or distracted, we change. When we focus and our emotional intelligence increases, we also change. Some of these changes are desirable, but most are not! Therefore, possessing a sustainable conviction over a long term turns out to be nonlinear. There is no standard method to sustain conviction. However, one must balance change and sustenance with conviction. New and complex subjects like data science and its integration in manufacturing require focus and engagement.


Human capital integrates data science, finance and creativity. This will levitate an organization’s performance.


Empowered staff with sustainable conviction can maximize profit and develop their employer’s performance in the long term!

 

An Idea in Brief


The joint use of data science, finance and creativity with behavioral science will be the harbinger of change for high technology and ambitious electroplating applicator. These trademarks are no longer nice to have, but are deliverables critical.


Real time reaction is the crux of the matter.

 

Use of data science and finance is about being proactive and making things simple. Behavioral science is about recognizing the values of creativity, data science and finance, and making it effective.

 

Agile organizations posses a lean production system. They become lean and productive by using proactive data analysis with innovative technology. These applicators write succinct operating procedures.

 

The four trademarks identified in this short paper are authentic methods to become agile and create an enormous surplus.

 

Note to Readers: Because of intricacy of the subject, brevity of time and confidentiality, the paper you read might drain the energy. The author desires a reader to revise the paper and enlighten on this matter.

 

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The metal finishing industry plates hard and decorative hexavalent chromium processes from 1920s. It is an acknowledged industry standard and preferred choice because of its exceptional physical characteristics. US Environmental Protection Agency (EPA) and Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) had listed chromium trioxide as a hazardous chemical because of its carcinogenic property.

 

Applications

Many aerospace components use hard chromium, the automotive sector primarily uses decorative and other sectors use both decorative and hard chromium plating deposits. A deposit thicker than 1.2 micron are functional (hard) and any lesser are decorative. The industry favors chromium because of its oxidation resistance properties. Among groups 4, 5, and 6 elements of periodic table we plate only chromium using an aqueous solution. Ionic liquids can deposit most of the transition elements. Aqueous hexavalent Cr deposit has exceptional tribological and corrosion resistance (not all formulations) properties. We plate the deposit on high strength steels and nickel alloys (with Wood’s nickel strike). This deposit exists in alpha phase, is crystalline and forms limited compounds or components with occlusion of hydrogen and carbon developing internal deposit stress (refer ASM Handbook for more information). The electrolytes’ low cathode current efficiency allows greater tribological properties. This is because the deposit has hydride and carbide compounds. These hydrides and carbides develop deposit intrinsic stress and effect deformation property of the deposit (Hooke’s law describes elastic properties of materials or deposit).

 

Extensive applications and good properties make environmental directions a challenge to meet. Before we get deeper, let us get a historical perspective.

 

History

Around 1910, a researcher accidentally developed the original hexavalent chromium plating formula comprising chromium trioxide and sulfuric acid. He assumed chromium trioxide was a trivalent salt until another scientist corrected the misinterpretation within two years.  

 

Research

From that time substitute methods such as trivalent chromium plating, cobalt alloy deposits, electroless Ni deposits with P or B alloys were developed and are a focus of continuing research. High temperature and room temperature ionic liquids for deposits such as trivalent chromium, niobium, aluminum, molybdenum is in study.

 

Alternate Choices

Chromium Plating

Trivalent Chromium Plating

Decorative trivalent and hexavalent deposits have similar properties because of the thickness limit and electrolysis mechanisms of the respective electrolytes. Electrolysis mechanisms change as electrolysis progresses and the deposit characteristics vary with thickness. There are scientific papers on this phenomenon. On hard Cr applications major variation is on macro-cracks, which develops after baking. When analyzing macro-cracks, a seldom adhered to practice is to compare the microstructure on transverse sections. Refer to ASTM E3 – Microstructure and Properties for more information. A few applications use nickel undercoat to negate the effect of macro-cracks.

 

Other Electrolytic Methods

A few specialists recommend electroless Ni-P, electroless Co – P and electroless Co as substitutes to hexavalent hard chromium plating deposit. But the author of this paper doesn’t consider these as dependable alternatives. Only electroless Ni-B (mid boron) deposit possesses tribological properties, but it doesn’t offer comparable wear and corrosion resistance properties of hard hexavalent Cr plating deposit.

 

Ionic Liquid Methods

Room temperature ionic liquid electrolysis is an effective alternate. Aluminum deposit offers many unique advantages. However, it is still an emerging technology.

 

Vapour Deposition Methods

There are two types of vapour deposition methods – physical vapour deposition (PVD) and chemical vapour deposition (CVD). We can apply CVD on several transition metals. Of particular interest to this topic are CVD deposits of Ta and Nb.

 

Thermal Spray Coating

On economy, versatility and diversity of options, the thermal spray coating processes is the best alternate to hexavalent Cr plating method. There are five different methods available in the market – oxyfuel wire (OFW) spray, electric arc wire (EAW) spray, oxyfuel powder (OFP) spray, plasma arc (PA) powder spray, and high velocity oxyfuel (HVOF) powder spray. Refer to ASM Handbook Volume 18 for more information on this subject. However, on many applications the line-of-sight characteristic will limit the thermal spray method. There is continuous research in this field, and recently a few companies have taken the processes to a new level.

 

Summary

Bottom line, trivalent chromium plating, vapour deposition, and thermal spray methodologies are operative substitutes to hexavalent hard chromium plating process. Application demand, cost and the required physical characteristics determine the value of a specific method.

 

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This paper explains Advint’s exclusivity from our competitors to the North American rectifier procurement agents.



Our rectifier sales vertical currently offers technological lead with substantial cost edge from peers, and we position us for the future of rectifier applications.


 

In the crowded rectifiers sales market, Advint distinguishes its leadership in the fundamentals, quality, technology and supply chain. Market surplus inspires customers to make wise choice by parsing quality and price benefit, and other technical factors.

 

This paper explains Advint’s exclusivity from our competitors to the North American rectifier procurement agents.

 

Electrolysis is DC power supply’s primary use. We begin by understanding the requirements of electrolysis and electricity. Other value adds are electrical and electronic necessities, automation, big data integration features and logistics. We made sales and customer services with a nimble format covering specifications check, electrical certification and inspection label needs, transportation and product warranty.

 

Electrolysis

Each customer need is different. On electrolytic application’s, due consideration of electrolyte conductivity and ionic mobility (and Ohm’s law) is important. We offer service to customers who want to go make a choice between insulated gate bipolar transistor (IGBT) and silicon-controlled rectifier (SCR).

 

Advint’s representative encourages considering ripple and maximum output DC amperes. On productivity be strategic on DC output amps, largest and smallest parts produced at a time, and the ripple tolerance based on electrolyte and electrode tolerance. An unsuitable choice can increase ripple, drive electricity consumption, and cripple productivity in the long-term.

 

Technology

Advint has partnered with a leading rectifier manufacturer. A professor scientist founded this company and had advanced a powerful team with a quality pledge. The supplier’s PRO series models meet UL and CSA’s inspection label standards. Their model’s MODBUS protocol and RS 485 communication enable automation and data integration of many parameters. Of course, most manufacturers offer similar features with an exception of Advint’s data integration feature. The most important distinction is the workmanship and rigorous quality system from the team on electrolysis, hydrogenation, electroplating and anodizing power supplies.

 

DC Rectifier

 

Supply Chain

We understand the customer wants great price and quality, with prompt delivery on the promised date. This is what we offer, and we do that with an attention on supply chain, customs clearance and transportation.

 

Future

Advint’s pivotal lead is our understanding of electrolysis and electricity.

 

We took simple but often discounted procurement process steps. Investments in artificial intelligence software to analyze disparate data and on digital ecommerce to make the buying process easy for our new and long-term customers are in progress. Advint offers a rebate for advisory services clients when they buy rectifiers.

 

Our rectifier sales vertical currently offers technological lead with substantial cost edge from peers, and we position us for the future of rectifier applications.

 

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The true plating capability refers to a process which performs as almost as expected. It executes with lesser labour, zero downtime, greater process control and with exceptional physical characteristics. Though it might appear simple, most job and captive plating shops seldom meet an effective realization of the said ability.

 

Challenge

Most processes have unique challenges. Cyanide and electroless electrolytes, precious metal plating like gold and silver, aluminum anodizing and stainless steel electropolishing need exclusive tactics. Cost metrics and process complexity varies within these processes.

 


An important holdup most stumble is accepting the status quo. Process failures, downtime, delays, etc. are perceived as a norm. As it occurred yesterday and transpires with others too!



Also, people with emotion become agnostic to methods, tools, concepts, and approaches. While, data science and artificial intelligence sans use of emotion.


This short paper aims to show a path toward a true electroplating capability.

 

Here is a simple infographic of vital elements to attain this goal:

True Electroplating

 

As shown in this graphic, our intent is at the core of our actions! Begin with intent to achieve infinite results.

 

We need knowledge and creativity with intent. The staff must have a comprehensive training on electroplating, lean, statistical process control, and total quality management. A good understanding of periodic table and electromotive force (emf) potential is mandatory. A process control is contingent on sampling and analytical techniques, and database integration with spontaneous communication and reaction.

 

Consider using 6 process development and control (PDC) tools as recommended by Advint’s earlier blog as an alternative to 7 quality control (QC) tools.

 

Plant Design and Automation

On no occasion reckon to aid a true electroplating feat with an inextricable and poor electroplating equipment design.

 

A nimble design with a correct choice of electrolyte chemistry, materials selection, engineering capabilities, rectifier controls and calculations such as ampere hour control, serial communication are indispensable.

 

Choose IGBT rectifiers for nickel, copper, silver, zinc and chromium plating applications. IGBT will be suitable for most anodizing applications, but sometimes a SCR rectifier or a half wave SCR rectifier will be essential.

 

Plating equipment and the manufacturer play a significant role in the plan of a new line. The project managers of most manufacturers do not have industrial plating experience. Under these situations, planning on processing, development tools, creativity and method become imperative.

 

True Electroplating Rewards


When a process performs, employee and customer satisfactions are at its zenith. You get to eat your competitor’s dinner.


How Can We Help

  • Advint’s prudent offering of advisory services empowers clients to achieve true plating capability.
    • Advint’s proprietary Time Change Management (TCM) tool aid metal finishers master productivity management, total quality management, and optimization of physical characteristics of the deposit.
    • We apply an algorithm software to deconstruct big data and conduct predictive analysis.
    • Advisory service includes backing platers in the project phase of electroplating plants.
    • The work supports research and REACH alternates.
  • Our online training course accommodates corporates and individual professionals.

 

 

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Acknowledgement of the influential in electroplating develops our learning of the fundamentals, and it improves our research.


There are thousands of contributors who served the electroplating industry and academia for over a century.

Who tops your list?

What did they do?

Why is it important?

What did we learn?


This short paper lists 8 innovators, two focused on electrochemistry and the rest on industrial plating (electrolytic, autocatalytic, ionic & aqueous). Their contributions enabled our understanding, improved our applications, and helped us to advance the technology.

 

Let us see who they are, when and what did they offer to the field and its benefits.

 

Michael Faraday

During 1832 Faraday published a paper relating the quantity of electricity with the amount of metal liberated at the electrodes resulting in two laws. When we think of electroplating, Faraday’s laws are probably the first to come to our mind. Mastering a process or shining at customer satisfaction does not end without due consideration of an electrolyte’s current efficiency and the feasibility of a deposit.

 

Walther Nernst

Nernst equation is the fundamental equation of electrochemistry and for the electrode processes. An ardent electroplating researcher shall begin and ensure a thorough understanding of Nernst equation and its concept. We can plate several transition metals, post transition metals, and metalloids. Some using aqueous electrolytes and room temperature ionic liquids, and most using high temperature ionic liquids. A modest approach to choose the electrolyte and the element for the deposition process is to comprehend Nernst equation and its concept. An interstitial or interatomic alloy electrodeposit choice is no exception to this subject.

 

Abner Brenner

Brenner conducted many studies on electroplating deposits. We conspicuously recognize for his preliminary contributions on electroless nickel plating invention around 1946. Though he got black non-adherent dendrites in the initial testing, his research allowed significant growth in electroless Ni-P and Ni-B deposition processes, and plating on plastics.

 

Richard Hull

Hull cell device is common in most electroplating laboratories. Most platers gain Hull cell testing skills or aspire to become good at it! Hull around 1930s invented a testing cell and derived a formula to calculate the effective current density of an electrolyte. Hull cell unit and its formula is quite easy to use! Is the design of the unit and its formula an ordinary achievement?

 

Oliver Watts

Professor Watts reported on 1931 his work on nickel plating bath comprising nickel sulfate, nickel chloride and boric acid at a higher temperature. Many used nickel-plating electrolyte using the same inorganic constituents at room temperature or at 120ºF. Watts was the first to report the benefits of thick and uniform deposit at 145ºF and 160ºF. Since then we began calling this electrolyte a Watts nickel plating solution.

 

Donald Wood

Wood was an expert in cyanide silver plating, and that is what he did for most of his career. We know him for his invention of chloride-based nickel strike bath during early 1940s. The Wood’s nickel strike formulation enabled the global industry to plate on all ferrous, nickel, titanium and aluminum alloys.

 

Donald Cook

Even if you are well read in the industry, you might not have heard about Dr. Donald Cook! Cook coined the term ‘metaliding’. Metal finishing industry did not see the effects of his research. But if I didn’t mention his name with others, it would be amiss as he is alike Nernst and Brenner. No one would have worked on more transition elements and diffused into others than him! His knowledge in electrochemistry and chemistry of halides was impeccable, and he distinguished the ins and outs of transition metals of group 3 to 11 of the periodic table. But his only focus was in high temperature ionic liquids.

 

Seymour Senderoff

We know Dr. Senderoff for his invention of spiral contractometer used in hard hexavalent chromium and nickel sulfamate plating applications to detect internal stress in the deposit. He worked for Dr. Brenner for several years and later focused on high temperature ionic liquid tantalum plating. It was my source of pride to continue on his research and improvise his formulation.

 

electroplating leaders

 

So, what is the learning?

Recognizing these pioneers and their work must transcend awareness and dwell on a deeper understanding of their explanations and research outputs.

Faraday and Nernst focussed on the fundamental of electrochemistry. Cook and Senderoff concentrated mostly on high temperature ionic liquid electrolysis (plating and diffusion). Brenner, Hull, Watts and Wood dedicated their research on commercial electrolysis. Nevertheless, all played a revolutionary role in electroplating applications.

 

Here are the examples of teachings from a few of these pioneers’ work:

Nernst’s invention allowed us to relate electrode potential, valency of the metal ion and current. Hull’s work brought to light Tafel’s, Butler’s and Volmer’s work. Wood’s invention signified electromotive force (emf) series and distinguished strike, flash plating, and plating. Cook’s and Senderoff’s developments emphasized the importance of eutectic temperature, phase diagram, liquidus temperature of salts, fluxing effect and ionic conductivity of electrolytes.

 

Hope you find this paper valuable and you dig deeper on these matters!

Post your comments and write about who tops your list.

 

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A recently published paper by a senior staff on a leading American magazine was unclear about the electroplating terms, like covering and throwing powers. Many times, we see vague interpretation and wrong distinction on these terms.

 

Advint’s online electroplating training and E-book offers right definition, explanation of identical terms and concepts. So, I’ll abstain from offering an elucidation here and write on the effects and recommendations.

 

The supplementary purpose of this paper is to emphasize the importance of correct interpretation of underlying electrolysis mechanism, terms, concepts of electrochemistry and electroplating fundamentals.

 

The confusion on these terms occurs when one draws a literary meaning on these words, reads leading technical magazines and science journals, and listens to veterans in this field.

 


Dr. Samuel Glasstone’s An Introduction to Electrochemistry delivers the clearest definition of throwing power of an electrodeposition process.


To correctly understand the terms, deeply observe acid chloride zinc or Watts nickel plating and cyanide copper or cyanide silver plating processes. Careful analysis of these electrolytes using a Hull cell will make clearness of these terms.

 


Handbooks and electroplating books frequently cannot document and analyze all developments, and now and then it misconstrues the depth of progress in the metal finishing field.


 

Confidentiality and hidden knowledge within the industry is the reason for such limitations. This limits awareness of all electrolyte properties and their formulations options with benefits. Many large organization’s operating procedures and practices also deter the best ability of a process.

We recommend you to question, test and re-consider critical attributes and formulations, including the references of Advint’s e-book guide to get a model electroplating routine.

 

Why is it imperative to comprehend properly?

Choosing a suitable electrolyte and maintaining the concentration of anions and organics will enable us to:

  1. improve product quality
  2. improve deposition thickness with due consideration for product geometry
  3. meet functional and customer criterions
  4. improve process control
  5. reduce cost associated with rework and under or over thicknesses
  6. minimize or eliminate problem solving time
  7. correctly comprehend fundamental electrolysis mechanisms

How can you learn the correct terms?

Advint’s virtual course E-book syllabus covers relevant electroplating terms and concepts.

We recommend referring authentic resources, test yourself by analyzing electrolysis and deposition mechanisms on various electrolyte formulations and metal deposits.

 

To the Point

In this short paper, we discussed why right construal of a plating term is important. We reviewed how to access the pertinent information and the reasons for confusions. A diligent comprehension of the terms will help advance the metal finishing capability to what it’s worth.

 

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The purpose of filtration goes beyond the removal of total suspended solids (TSS) from electrolytes like chromium conversion coating, electrolytic plating, electroless plating, anodizing, electro-polishing, and immersion electroplating processes.


Though filtering an electrolyte is the prime aim, the flow of electrolyte, its velocity, uniform distribution and consistency effects the deposit physical characteristic and morphology.


 

In this short paper, we will review the apparent and not so obvious functions of filter systems and recirculation of electrolyte. We will also look at the filtration merits for processes such as Watts’ nickel, electroless Ni-P, electroless Ni-B, precious metals plating such as gold and silver, hexavalent and trivalent chromium conversion coatings, immersion plating and plating on plastic. We will assess design criterions for filtration, properties of electrolytes and potential benefits of optimized filtration systems regarding deposit morphology.

 

Electrolyte Properties

Not all electrolytes have similar filtration or flow requirements. A Watts nickel electroplating electrolyte and simple cyanide gold plating electrolyte differ in the formation of suspended solids and the intensity of flow. The volume of the solution and turnover of the components require horizontal disc filter system for nickel plating, whereas most precious metal plating solutions would require cartridge filters. Horizontal disc filter systems design is over 150 years old and had stood the test of time and quality. In cartridge filters, size and pore size are important. Here the distinction is the property requirement of electrolyte, where concentration of metal ions at the vicinity of the cathode is influenced by flow (not the only variable) and is related to the current efficiency of the electrolyte. With Watts’ nickel, we require a vigorous agitation and flow when compared with cyanide gold electrolyte, which requires less agitation and a gentle flow.

 

System Design

To ensure the filtration is effective and flow is uniform, we must consider plumbing the inlet pipe near the bottom of the tank and the outlet at the diagonally opposite end of the top. It is important to ensure never the electrolyte flow directly impinges on the part, as this will negate plating in that area. A simple reference to the supplier’s technical data sheet will help determine the motor capacity of the filtration system (flow rate per hour).

 

Deposit Characteristics

The filtration system’s primary purpose is to filter the solution and remove TSS. Sometimes filtration might not be necessary, and recirculation might suffice. On most applications, consistent flow, required velocity, optimal distribution will help deposit morphology and crystal growth. Resistance created by the cartridge alters flow. Change in velocity of the flow and the distribution pattern effects crystal habit, domain growth, and continuity of the deposit. Tribological and corrosion properties of any deposit is improved and are consistent when the growth continues without interruption and the growth rate or rate of discharge of ions are steady.

 

Electroplating Filtration System

Summary

In this paper, we saw the importance of filtration, options available in the market, the vital reasons for proper design and specifications of the system, and the benefits of having consistent flow and distribution on various electrolytes.  We discussed distinct properties of acid and cyanide-based electrolytes, metals with high and low electrode potentials (nickel and gold), and their respective filtration requirements and benefits of specific choices.

We recommend process engineers to assess the simple but important filtration system on aspects such as systems design, required flow functionality from electrolyte properties perspective. And interpret deposit properties like tribology and corrosion or others when determining flow velocity, distribution and consistency.

 

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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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Venkat Raja
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May 1, 2021
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