Nickel Plating Bath Composition

A nickel electroplating bath for obtaining a satin-finish which comprises a solution of acidic continuous phase nickel salt solution, an alcohol soluble poly-amide resin and polishing agent dissolved in bath. The polyamide resin is a member selected from the group consisting of a co-polymer of dimer acid and an aliphatic amine, a co-polymerized nylon and a modified nylon. The electroplating bath preferably contains a cation surface active agent selected from the group consisting of an aliphatic and/or aromatic Quaternary ammonium salt and an aliphatic and/or aromatic fluorosulfonylamine Quaternary ammonium salt. The use of the electroplating bath provides a means for obtaining a uniform satin-finish nickel plating surface on the material plated.

Acidic nickel electroplating bath composition obtaining a uniform satin finish metal plate surface on the material plate surface as below:

1. Nickel 25 to 170 gm/lt
2. Polyamide resin dissolved in low molecular weight and alcohol have 1 to 3 carbon atom: 1 – 10,000 ppm
3. Polishing agent: 0.1 to 40 gm/lt

Nickel is dissolved and forms a continuous aqueous phase solution and poly-amide resin is dispersed in aqueous phase to form a stable emulsion.

Bright Chrome Plating in Plastic

Bright chrome can be applied in metal or in plastic. If bright chrome is applied in metal it usually use chrome plating process that is usually use electric current and chrome solution to make the chrome ion can plating into the surface of metal. On the case of this electroplating process, some condition should be controlled like the concentration of chrome III should be in maximum level, and if possible there is no chrome VI content on the bath. Even the chrome VI always there but by control of certain condition, chrome VI level can be minimize.

Otherwise if we doing by electroless chrome plating, we don’t need any control of chrome VI concentration because this method don’t use electroplating anymore but use like spray chrome paint or other way to coat chrome directly into the surface of metal. The same if we plated chrome into the plastic surface, we also don’t need to control of chromium VI, because we don’t use chemical solution first to do chrome plating. Plating on plastic may just conditioning the plastic surface in order chrome agent can be plated dirrectly into the plastic surface. Experience people already made this with their knowledge and don’t need any control of chromium VI. But if you use by two step of coating of plastic surface, other possibility may can happen, such as first use electroless coating to plastic, for example nickel plating use electroless method, and the next step use chromium plating using electroplating with electric current. For this you must control the chromium VI in the bath.





To make bright surface can be done in the same way, that is to polished the surface after chrome plated. The different may can be how the way to polished of the surface. Rubbed material may can different for plastic surface and metal surface. For plastic need more soft than for metal surface. The current technology we supposed that coating on plastic will no need of electroplating process anymore but only electroless plating. You can survey to the market, many kind of plastic with chrome plated but very cheap price, usually Chinese product. If they do this with electric energy, the product will impossible sell in very cheap price.

Black Chrome Color

Black Chrome color has developed long ago, long technology of using general process can easily produce black chrome color but the result is not satisfied. The coating surface look like hard and brittle, easily to crack. Black chrome finishing can use by oil dipping. The general process of electroplating before chrome plated over the surface is using nickel plating first as base coated material.

Newer technology of black chrome process by using of trivalent chromium bath Cr (3+), Black chrome technology is use right chemical in order the surface of coating become black. Electric current just helping the chrome ion become plated on the surface. Additive chemicals such as acetic acid make the coated surface become black because the available of other acid such as acetic acid and barium acetate make the chromium ion plated turn into black.

See also black chrome plating product: Chrome Plating

Supplier of black chrome product may on below :

Polution Control of Chrome Plating

Environmental protection become very strict currently and chrome plating industry include of one Industries that can contribute to pollute environment. To lessen on polluting environment several tips on doing electroplating should be done:

• Reduce Dragout and Water use: Minimized dragout and to minimize extent possible, return residual dragout to the process tank.
• Install dragout racks over tanks or drip guards and return solution to process tank
• Perform initial rinse tank with return of solution to process tank
• Avoid solution disposal by minimizing bath contamination and using available maintenance technology recycle wwtp (waste water treatment plant)
• Minimize Chromium fume to air emission to workplace and community. Use less toxic substitute technologies where applicable.
• Use developed technology on process waste water for example ion exchange technology, ion transfer technology or membrane electrolysis.

This one is diagram of ion transfer technology that used in Navy testing.

ion transfer technology

Other Site:

• Chrome Plating
• Gold Plating
• Anodized Aluminum
• Adhesive Type

Electroplating Plant

electroplating plant

Electroplating plant is should be arrange in serial work, because each process need different chemicals and from batch to another batch need rinsing in order not contaminated chemicals on the serial batch. Electroplating plant should be designed in semi batch process, can’t run in continuous process, because before and after electroplating process the object need certain treatment. Automatic process is not on the electroplating work but automatic mean every batch is doing by robot, so people just control of every step robot work and the quality of all process, including the quality of chemical solution bath concentration.

Each bath chemical solution is purpose for certain product, for example in producing chromium plating, there are bright chrome plating, black chrome plating , semi dull chrome plating, white chrome plating and any other chrome plated color. Only the preparation of base metal may can have the same process, for rinsing and polishing of each color of chrome plating can be in different method even can use the same equipment. Waste of rinsing and cleaning can be mixed for various chrome plating color, and need further waste treatment process, to make environment friendly.

General order of electroplating process such as follow:

• Preparation of base metal
• polishing
• rinsing
• chemical cleaning
• rinsing
• electrocleaning
• rinsing
• Electroplating (ei. chrome plating)
• Rinsing
• postplating treatment.

Each of different process which use different chemicals must use different bath but for process which use same solution like just water may can use same bath, it is depend on the plant layout. Each plant can be different layout.

If there are any other electroplating purpose like Nickel plating which use different chemical solution, this need different bath, other wise they must clean the bath every do other kind of plating, and for this can be inefficient work. The plant which apply of many kind of plating can be arrange in serial process and parallel process order.

Operating Conditions

Operating Condition of Electroplating Process

Bright Plate can be reliably obtained by properly coordinating temperature and current density within definite limits, taking into account the chromic acid concentration of the bath. The operating condition for bright plate should be on the temperature range of 25– - 55 C degree with current density range between 5 -– 25 A/dm2 for solution containing 250 g/l CrO3. For example to produce a bright plate deposit from a solution containing 250 g/l chromic acid and 2.5 g/l sulfate at a temperature of 40 ^oC, use cathode with current density between 3.1 and 15.5 A/dm2 but at 45 ^oC use current density about 50 % higher.

Plating at higher temperature and current densities has been proposed for hard chromium plating and porous chromium plating. This idea has been applied successfully to plate a small articles, but the power required for plating larger objects may be prohibited or unavoidable.

Chromium plating speed was vary depend on the chromium concentration on the bath. Billfinger suggests the use of higher temperature and current densities, combined with lower ratios of chromic acid to sulfate, to obtain higher plating speeds for hard chromium plating.

Throwing Power

Both the throwing power and the covering power of chromium plating bath are poor compare with copper or nickel plating bath. The conductivity is high but reduced by such impurities as iron and copper. The cathode polarization during chromium deposition is relatively constant and substantially the same as that obtained during electrolysis of the same concentration of pure chromic acid without chromium deposition. The major variable connected with throwing power in bright chromium plating are the current efficiency and the bright plating range. If a given set of condition gives the widest possible bright plate range and the plating is done at an average cathode current density near the upper limit of current density for this bright plate range, the optimum throwing power will be attained.

High Throw Bath

High-ratio baths containing relatively high concentration of organic acids have been developed which exhibit remarkable throwing power or covering power over bright nickel, almost as good as that of bright nickel bath themselves. These solution operate at lower current efficiencies to produce thin bright plates of good decorative value. It is a characteristic that the coverage increases with the time and the plate continuous to spread into the low-current-density area with longer plating. Thus plating times as long as 5 to 10 minutes are recommended instead of the 2 to 3 minutes often used for decorative plating.

Other articles:

• The best metal for chrome plating
• Plating small parts 

Hardness Test of Coating Plate

Steel coated with chrome plating or with nickel plating will have different hardness and looking. After coating with chrome or nickel then the surface become more interesting and stand to corrode. This is the basic purpose of steel coating. The stand to corrode and how long it can be stay on the surface depend on the dept of coating and the strength of coating material on the plate surface. One of how to test the strength of this using hardness testing. This tool work is use a fixed forced and given identifier, that show the harder of surface material.

The value of hardness test is identified by measuring the depth of the area of the surface by using several methods. One method to identify of hardness is use Rockwell hardness test method, this method is the most commonly used to test hardness of steel surface.

The standard of hardness is illustrated by the most hardest material is diamond which have hardness value of 10, other material will have below this.

Soft: scale value = 1 – 3
Medium hard: scale value = 4 – 6
Hard: scale value = 7 - 10

Thickness Measurement of Plating

How to measure thickness of Plating

Coating thickness can be measured by some tools that using one of these method: x-ray fluorescence, coulometric, beta bacscatter, magnetic induction, amplitude eddy current and phase sensitive eddy current. To make sure of what kind of thickness you will chose better ask to the supplier.

To measure the coating thickness on the plate, you can use x-ray fluorescence tools. This tools can measure the thickness of coating thickness of chrome, nickel and copper plated. The kind of coated of each coating material is no problem, like decorative chrome plating, black chrome, bright chrome, bright nickel plating. Because this tool to measure the thickness using x-ray fluorescence that work only on the base metal.

To measure the thickness of coating surface can use thickness coating gauge such as on the picture below:

Electroless Nickel Plating

Electroless Nickel Plating, what is that? Electroless plating is an auto catalytic chemical technique used to deposit a layer of nickel phosphorous or nickel boron alloy on a solid work piece, such as metal or plastic. On this process is no need additional electric current because the electric charge is merging from the substance itself. The principle of work of this process is the present of reducing agent, for example hypophospite react with metal ions to deposit metal.

Electroless nickel plating often use in various type of parts to protect against wear and corrosion. Uniform deposit of nickel useful for hydraulic cylinders, worm feeds, gears, bellows, shafts, chain belts and other close filling components.

Nickel plating on subject can be doing in two kind of process, using electroplating method and can do by electroless nickel plating. For electroless nickel plating or coating then be classified in accordance with the thermal treatment applied:

• Class 1 = no subsequent heat treatment: A bake for hydrogen belittlement relief is not considered a heat treatment.
• Class 2 = using heat treated to obtain required hardness: this can be applied to all metals not affected by heating up to 260° C or above.
• Class 3 = by non heat-treatable, and use beryllium alloys to improve adhesion nickel plating deposit.
• Class 4 = heat-treatable, use aluminum alloy and heat applied to improve adhesion nickel deposit.

Quality of Plating Thickness

Beside divide into the class on the process do, electroless nickel plating also divide into the grade of coating thickness. There are three thickness class:

• Grade A = 0.127 mm
• Grade B = 0.254 mm
• Grade C = 0.381 mm

Hard Electroless Nickel Plating

If use alloy with low phosphorous, plating utilizes a unique bath providing coating hardness up to 60 Rockwell. This result can be similar with hard crome Hard, with the advantage of a uniform thickness inside complex configurations, as well as outside. Low contain of phosporous have excellent result and resistance to corrosive and high pH chemicals.

The quality of electroless nickel plating may not stronger as using Nickel electroplating, but electroless nickel plating will improves the quality of components. Tight manufacturing tolerance can be achieved as the electroles nickel is deposited evenly on the surface of the parts. It can be also used to improve the surface of a component so that it is back within the specific tolerance, and provide a surface that allows post finishes to be carried out effectively produce bright surface coating.

Some example product of Electroless Nickel Plating as on the picture below:

Electroless plating product

Reaction on Electroless Nickel Bath

Electroless nickel bath contain of nickel ions, reducing agent, complexant, neutralizer, buffer, stabilizer and brighteners.

The reation on bath as follows:

1) NiSO4 + H2O → Ni2+ + SO42 - + H2O
2) NaH2PO2 + H2O → Na+ + H2PO2- + H2O
3) Ni2+ + H2PO2- + H2O → Ni + H2PO3- + 2H+
4) H2PO2- + H2O → H2PO3- + H2 (by catalist)

Next articles:

• Electroplating Process Flow Diagram
• Electroplating service
• Nickel plating brighteners 

The Best Metal for Chrome Plating

Metal want to be plated can be vary some of recommended from plating service industry can use aluminum alloy, Brass, Bronze, copper, mild steel, stainless steel, zinc die-casting, pewter. The chrome plating process itself can be do as follow sequentially:

• Polishing (preparation for plating)
• Soak Cleaning (can use alkaline cleaner)
• Surface activating
• Copper plate
• Nickel plating
• Chrome plating

The result of chrome plating is depend on the base plate condition before electroplating process applied. Poor adhesion of chrome plating can be happened because of the bath solution concentration or because poor base plate plating. Preparation of base plate is needed in order can best chrome plating. Bath concentration of the chrome plating bath should be checked before the plating is running, this is part of quality control of laboratory person job. Poor adhesion result of chrome deposit will immediately separating from the substrate after the object take out from the chromium bath. This can occur from peeling or blistering of chrome layer.

Bad Chrome Plating Deposit Causes

To test the quality result of chrome deposit usually by immerse on boiling water, until the object temperature up to reach boiling water temperature. Poor adhesion will likely show up as blister in chrome deposit surface. Other method to test the deposit quality is by grinding the deposit with 45 degrees angle and and examining the edges under microscope for to see if any flaking. Poor adhesion can also occur if the electric current flow is too high. Some deposit fail can cause of some of the following problems:

• Improper cleaning, some grease can withstand the molecule adhesion on the plate. For perfect cleaning can use organic and inorganic cleaner.
• Bad plate surface activation, see on the electrocleaning (cathodic cleaning) and chemical cleaning for pretreatment object preparation.
• Not perfect rinsing, make some dirt still stick to the object
• There is oil or organic material on the bath function
• Bad electric conductance on the process can because of any intermittent electric connection
• Anode already rubbed and dissolved on the bath solution
• Too little concentration of electroplating additive
• Bath temperature not in optimum condition check for this in baht temperature control
• Temperature, bath concentration of chrome plating operating condition should be controlled properly
• Postplating treatment after chromium plating can also make bad result of chrome plated.

Type of Paint

The type of paint actually any two kind of paint: water paint such as water color paint, polymer paint water based and oil base paint. Water color paint can use for drawing in paper or for interior wall decorative, to make this paint stand to water splash or humidity it should be covered with coating material, water paint also can use for indoor of house but as I know the color not good, polymer paint usually water based after paint already dried then paint changed into polymer and can’t dissolve in water anymore. The quality of this paint actually on the quality of hardener that mix in the paint. And other paint is oil paint, this paint can use for wood, steel or metal, and also can use for wall.

Type of Paint Product

The type of paint product can be vary usually base on the what much request from the market. Here are some of paint product available on the market:

Latex Paint, latex paint water based can be used on both interior or exterior projects. Latex is quick drying, easy clean up and the most part is simple to use. Beside for paint latex usually use for adhesive and raw material of car tire.

Alkyd paint, alkyd paint can be oil based or alkyd base paint. Oil base paints are durable, flow nicely and depending on the color tend to leave the least amount of brush and roller marks.

Epoxy paint, epoxy paint looking for type of paint with endurance, epoxy paint would be your best choice. Epoxy paint do produce inherent problems that other coatings don’t have.

Trim paint, some manufactures make this paint designed specifically for house trim painting. Trim paints tent to have excelent durability and adhesion along with sheen of either semi or high gloss finished.

Elastomer paint, elastomer paint usually use for exterior painting walls and trim. Raw wood, masonry along with concrete type substrates tend to give elastomeric paints a good pours surface to hold onto.
Emulsion paint, Emulsion paint like other kind of paints, are the combination of water base and oil binding pigments. Emulsion also include a number of other substance.

Anodized spray paint and Chrome Paint, anodized paint and chrome paint usually pack in spray can because the user only use a small quantity but for huge quantity you must buy a special order in order get in big bottle package. Anodized paint is mixed with aluminum oxide and sprayed in the surface of metal to cover the metal and have attractive color. Chrome paint is paint mixed with chromic acid, this paint is used to cover metal from corrode.

Spray Paint and other Package

Paint product in the market available in two kind of package, product with spray can and in large can. If you need many volume of paint you can buy big package usually use big can or bucket.

Other Site:

• Chrome Plating
• Gold Plating
• Anodized Aluminum
• Adhesive Type

Chrome Paint

Chrome paint is make the object surface being paint become shiny like mirror. Chrome paint usually in spray type. Some chrome spray kit allows you to put a chrome or custom colored chrome paint finish over any surface. Goods that already chrome painting look like have applied like bright chrome plating.

Chrome Paint

Chrome paint is very fluid and properly applied and not top coated, using spray chrome paint you can make a thick layer but can’t stick very strong, but use chrome plating, coating surface only few micron but stick very strong depend on the electric current arrangement. Chrome paint can be cover by clear coat but the bright of paint will less loses, less shiny.

Application:
Chrome paint usually use in automotive decoration. It can be applied over any type of material, such as metal, aluminum, plastic, wood polycarbonate.

chrome paint for motorcycle

Other Site:

• Chrome Plating
• Gold Plating
• Anodized Aluminum
• Adhesive Type

Free e-book of Nickel Plating Process

To understand the theoretical about Nickel plating process, you may can download from the internet freely. The book is discussed all about Nickel electroplating with good design and good looking picture. But the point of this book just theoretical of nickel plating not practical use, so don’t try base on the theoretical because many parameter still not tell on the theory, what discussed on this e book also already discussed on this blog about 10 years ago. The theory is just for your reference if you are running plant of nickel electroplating. The real hand book should be from equipment supplier how to run the machines.

The book actually complete contain such as:

• The role of addition agents
• Bright nickel plating
• Nickel Brighteners
• Anticipating Agent
• Anti pitting agent (wetting agents)
• Semi bright nickel plating solution
• Sulphamate nickel electroplating Bath
• Anode for nickel plating
• And many other discussed about nickel electroplating

If you need addition information about nickel plating you can download this e book freely, but on this blog only talking each of the problem and little about nickel plating theory, not in detail.

Calculate Surface Object Plated

Here is how to calculate the object to be plated.

The price of plating to sheet metal sometime very difficult if you just calculate as it is. Because the object to be plated often time is not regular form. For example if you have goods to plate with box form or cones form you can measure each size and you can use mathematics calculation. See here about how to count surface area of many kind of cube and tube formula.

Those are a regular form, what about irregular form like motorcycle engine block, how to calculate this? Any idea? If you use mathematics to calculate irregular form it is impossible even you use integral function to calculate surface area. Electroplating service company will not use integral formula to calculate the surface area, this can be very expensive because need mathematics engineer that must pay with high price and need long time. The practice way to calculate the surface of irregular form is just dipped in the water that already fill with certain volume in certain place like in box or in big tube. The initial height is record after the object dipped will rise and the final height is record too. After this you have the difference between initial and final height, after then you can use mathematics formula.
So to calculate surface to be plate is very simple, not like people says that to calculate can be complicated, because they are not practitioners.

The price shown on the table, plating price can be calculated per m² of surface or more realistic is calculated per kg coated material use. The table below shown for chrome plating, nickel plating, silver plating, gold plating, bronze and brass plating.

Table of Plating Price

Chromium (VI) must be Controlled

Worker must be provided with complete safety equipment in order can work in health condition for long time in chrome plating industry. Chromium plating is purpose to covered metal in order have good properties and stand for long time period. Chromium plating on the process will expose chromium fume. The problem when chrome (VI) or hexavalent chrome also vapor even this gas can cause severe health effects include lung cancer if long time exposed. Exposure limit from OSHA’s for Cr VI about 5 µg/m³ maximum 8 hours exposed. Chromium VI on the bath can be created by the temperature increase that can be affected by the electric current that flow on the bath solution. The character of hexavalen chrome is more easily to vapor compare to chromium III that more stable on the bath solution.

How to control the concentration of Cr(VI) 

To overcome the availability of Chromium (VI) we must know what or where this substance come from. Several source that developing Cr(VI) on the workplace.

Full Face Masker

Masker

1. This electroplating process is use electrodes (anode and cathode) that is connected to DC electric current source make each electrode developed gas and this gas then merge to the surface bring chrome substance Cr (VI) together, causing bad smell and make chromium concentration drop because vapor to atmosphere. The increasing number of chrome gas will generate higher electrical current in bath, longer plating time, higher surface tension and bad chrome coated in the subject. Chromium vapor can take out using fume hood to remove gas in the workplace and then gas is treated first before blow out into atmosphere.
2. To much vaporization can make spill and make more chromium vapor. This can be controlled by reduce the electric current that applied on the process.
3. Use other raw material in order not produce Cr (VI) too much, for example chromium (III) is less toxic than Cr (VI), for this purpose, supplier of chromic acid may can talk much more about the quality of this substance.
4. For person who work in this plant must use Personal Protective Equipment (PPE) for this purpose must use masker or full face masker.
5. Use hands glove on working with chrome plating process to avoid direct contact with skid, and use special chemical cloth for work that usually is designed special for working in chrome plating areas.
6. Put all dangerous sign and hazard symbol like use gas masker or must use hands glove for work and so on.

Chrome Plating Failure Can Make Aircraft Accident

The Story of Aircraft Accident

Chrome plating is good metal surface protection, but it should be used in correct place and application. We can’t coat all metal using this method because its look like better performance. Nowadays people like to crome their motor bike engine and all of part of their bike in order look good performance. This is not wrong but can not be applied to all part like engine parts. This can be dangerous, you can see the story of aircraft accident because of their engine part apply of chrome plating.

aircraft accident

The story are as follows; aircraft with four engine, propeller driven transport plane had just touched down when the left main wheel assembly separated. This plane slewed off runway and fire merge on the wing and engine of the left side. However the result of detail investigation, inter granular fracture was observed without evidence of fatigue striations. It was concluded that trunnion arm had failed because of corrosion and cracking.

Trunnion arm was made from a fine grained, through hardened and tempered 4340 steel. It had been subjected to excessive wear in repair, and during the overhaul it was known that already chrome plated to bring the dimensions can fulfill the specification. After use and worn trunnion arm back to the original level. Found that beneath the chrome plating and adjacent to the fracture, a regular pattern crack was found, but don’t continuous to the chrome plated, this indicate that this were not due to plating crack. The crack actually just 0.5 mm in depth, which caused by overheating occurred during grinding before hard crome applied. So chrome plating need perfect prepare before applied so some fist treatment like grinding is must be done before it being chrome.

Bath Function on Chromium Plating (2)

The condition process of Bath function:





As already discussed on the first bath function of chrome plating that the solution on the bath contain chromic acid and sulfuric acid. The concentration of chromic acid on Bath Function about 50 g/l up to saturation (about 1000 g/l) can be used, most commercial baths are operated between 150 and 400 g/l. Still higher concentration give very low current efficiencies. The important requirement is the ratio already mentioned. Usually chromic acid solution will down after use and on the critical concentration chromium metal will bad stick to anode.

Baths containing 250 g/l chromic acid have a slightly higher current efficiency than more concentrated solution. They also have a lower conductivity and therefore require a higher voltage for a given current density. The more dilute bath are also more sensitive to addition or removal of catalyst acid radicals from drag in and drag out. Hence they more concentrated solution are favored for decorative applications and the more dilute baths for heavy hard chromium plating, but there are many exceptions.

Siliconflouride has had considerable use as a catalyst in chromic acid baths since it was first proposed. Such solution was difficult to analyze and maintain.

Black and Color Chromium Deposits

Many attempts have been made to produced "black" chrome plating, and such deposits have been used commercially. They are usually dark grey rather than black, however, and all dull or mat chromium deposits color seem to turn bright metallic rather readily if exposed to much abrasion or wear, in spite of the hardness of the metal. Oiling and other final treatments give grey or dull deposits a blacker appearance. An early "black" chromium plate was produced by using a high current density in a cold bath containing principally chromic acid and acetic acid.

Modification of this process for "black" chromium plating has been proposed. Current interruption and sulfate-free chromic acid with fluoride or complex fluoride catalyst have been used. Some practical of this process should be make trial for several changes in parameter in order feel confidence on produce black color of chrome deposit. For other color of chromium deposit should use different bath chemicals solution rather than chemicals for black color deposit. For color chrome deposit should find other kind bath solution that can produce color chrome deposit like for decorative chrome deposit. The method to produce color chrome deposit can be in two stage, for example by first plating using nickel plating than the subsequent plating using chrome plating, or the first layer use copper substance that the subsequent layer use chrome plating.

Trivalent Chromium Baths

Historically, trivalent chromium baths have been the first and favorite approach to chrome plating, but they have always failed to match the reproducibility and dependability of chromic acid solutions, as has already been discussed in the section on theory.

The United States Bureau of Mines developed a process for the electroplating of pure chrome to meta from the ore from ferrochromium. Using a mixed bivalent and trivalent chromium sulfate solution, but the process has not been adopted successfully to plating purposes. A two-compartment cell is used at the Union Carbide Corporation, Marietta, Ohio, plant, and continuous operation on a large scale seems necessary for good result. In another review of the operation that low efficiencies always prevail during the startup of a cell.

Success was very limited in effort to utilize such baths for electroplating. A chromium ammonium chloride solution was used for brush plating. Better results in brush plating were obtained with Gregory's salt, ammonium chromium oxalat.

More recently there has been an effort to commercially the use of chromium chloride solution in or containing, organic solvent. The deposits are darker than those from chromic acid solution, and some chlorine gas is generally evolve at the anode. Only decorative deposits are being considered.

Chromium Electroplating

1. THE PRINCIPLES of ELECTROPLATING

Article Contents:

The Principle of electroplating

Decorative of hard chrome plating

Thickness Control of Plating Deposit

Preparation of chromic acid

Bright Chrome Plating

Black Chrome Plating

Temperature Control

Chrome Plating Result

Dull White, Black, Bright Black, White and Gold Color

Chromium Electroplating or people just say chrome plating is a process of metal coated using chromium substance or chromic acid. Why use chromium substance to cover metal surface? Chromium is a metal substance that resistant to corrosive while other metal like steel are easily to corrode affected by wet air. Chromium can’t be deposited from solution only chromic acid (CrO₃) and water. There must be present in bath one or more acid radicals which act catalyst to bring about or aid in the cathodic deposition of chromium. The purity of chromic acid used is often not specified or established and yet the nature. The end of the process chrome will coated the surface of metal.

Chrome plating is not difficult covered on the part has been properly cleansed using the following requirements met:

• Preparation of the chromic acid (CrO3) solution..(Do not acquire the hydrogenated ( H₃CrO₄ ) chromic acid crystals)
• Temperature control of the bath (plating solution)
• Preparation of lead anodes (peroxide)
• Agitation method of the bath (bubbles)
• Plating current density control and duration (controller)
• Ventilation (for safety)

All that remains is the requirement of time - so don't let the apparent complexity of the task discourages you because the results are very worthwhile, indeed.

I have studied the industrial processes involved, reduced them to pint-size applications for model engineering, and experimented enough to be able to tell you what works. We have a lot to learn and the process has been laid out for you in ten easy steps. So, here we go!

2. DECORATIVE OR HARD CHROME PLATING

All chromium is about the same hardness; 800 to 1000 VHN - very hard! The main difference lies in the thickness of the deposit of chrome coated on the metal.

For decorative purposes, chrome sits best on nickel which itself adheres very well to copper - this combination also offers the best corrosion protection resistance more better. Decorative chrome coating thickness will vary from a few hundredths of a mil to 1 mil. The mirror finish will only be as good as the finish you put on the surface before you put on the chrome.

For functional purposes, to take advantage of the extremely low chrome coefficient of friction, or for wear build-up (bearing surfaces or pistons, as examples), hard chrome is plated in thickness as required from 1 to 50 mills.

When used as a bearing surface. Chrome must be micro-finished (more on this later) and will then provide a coefficient of friction lower than any other metal when used against steel, iron, brass, bronze, babbitt, or aluminium alloys. Do not use chrome against chrome. Because chrome is also much harder than casehardened steel, we then have a perfect set-up for longwearing working surfaces. Chrome will resist mostly all organic and in organic compounds and acids, except hydrochloric acid (muriatic).

3. CONTROL OF THICKNESS OF DEPOSIT PLATING

Given fixed parameters for temperature, plating solutions, anodes, set-up, and current density, thickness is a function of time. Expect around .75 to 1.2 mil per hour of plating time.

I have plated up to 20 mills successfully at home - admittedly this was by accident because I was aiming for 3 mills deposit to refinish a piston! It had previously taken six hours using a particular chromic acid solution to deposit 3 mills of excellent chrome. I thought to shorten plating time I would increase the current density from 600 mA to 800 mA and the temperature of the solution was tweaked from 450 ^oC. to 500 ^oC. (113 ^oF to 122 ^oF). I then plated, with agitation, for five hours and wound up with an hour-glass shaped piston, due to a 13 mill chrome deposit measured at mid-skirt level and 21 mils on the edges (formed by the bottom of the skirt and the piston crown).

Let that be a lesson to all of us: Never change more than one parameter at a time. Subsequently, grinding of the same piston was successfully carried out; which attests to the excellent adhesion of the chrome to the base metal (steel) as prepared earlier.

Of course, the piston was then lapped to a perfect fit in the re-lapped bore (no rings involved in that 0.020 cu.in. engine). We'll come to the grinding and lapping notes later. Chrome will lap to a superb finish, to a degree of precision obtainable by no other method and limited only by the machinist's patience and skills.

4. PREPARATION OF THE CHROMIC ACID BATH

NOTE: The chemical formulations given in this article are in avoirdupois ounces per gallon of solution (avoir. oz./gal). To convert these to metric measure, simply multiply the oz/gal number by the conversion factor of 7.5 to obtain grams per litre.

4.1 BRIGHT CHROME PLATING

The formula for Bright Chrome Plating use the basic formulation of 100:1 chromic acid/sulphuric acid proportions:

• Chromic acid crystals = 33 oz. (936 grams)
• Sulphuric acid fluid = .33 oz. (9.36 millilitre)
• Distilled (or demineralized) water to make 1 gallon (3.79 litre).

Of course, you can vary these proportions in accordance with the quantity you wish to make up. So, to make up one pint for small work, simply divide everything by eight The dilution ratio of the sulphuric acid as purchased has to be taken into account and the amount used in the bath must be one of pure H₂SO₄ to 100 Cr0₃.

Be very accurate in this process; and:

ALWAYS ADD ACID SLOWLY TO WATER -- NEVER ADD WATER TO ACID

If you have access to demineralized water from your home dehumidifier (of course, clean filter if required). This is a good substitute for the recommended distilled water.

Also, I recommend the use of surgical rubber gloves when handling any of the chemicals called up in this article. Pharmacies (Chemists) carry them and they are much easier to replace than the skin of your hands.

The chromic acid crystals yield about 52% pure chrome metal. For reasons, which must remain unexplained at this stage, a freshly mixed solution will only deposit passably good chromium. The same solution, like a good wine, improves with age... So use it for experimentation when first mixed, before you undertake any serious plating - I keep mine in a sealed glass container and it is good for years. Filter as required between uses - plating current will be around 0.75 A/sq.in. For bright chrome and up to 1.4 A/sqin. for dull 'hard chrome'.

4.2 BLACK CHROME PLATING

Black chrome plating can also be plated in the same way and still have similar characteristics to the bright chrome. For aesthetic or anti-reflective applications, it may be preferable in some cases. I have not yet used it, but the formula is as follows:

• Chromic acid 33 oz (936 g)
• Acetic acid = 28.2 oz (800 g)
• Barium acetate =1.0 oz (28 g)
• Distilled (or demineralized) water to make 1 gal. (3.79 litre).
• Operation of this bath will be at 90 ° to 115 °F (32.2 °C. to 46.1 °C.) and at a current density of 0.25 to 0.63 AIsq.in. (More on how to set this up later). 

Find Chemicals Supplier For Electroplating Solution:

4.3 TEMPERATURE CONTROL

Temperature is critical for good (or any) results. This is best maintained automatically by using a thermostatically controlled electric heater right in the bath. A simple and cheap expedient for this requirement is to use a tropical fish-tank heater available at any pet store. And, while you're there, pick up a fish tank air pump, plastic piping to suit, and one air valve control, too.

The 115 V heater comes in a quartz tube with a temperature control knob on top. This acts on a bi-metal strip contact tension and can easily be cranked up to maintain the required 45 °C. to 50 °C. (113 °F. to 122 °F). A thermometer covering this range is also required.

It is important this temperature range be maintained throughout plating times.

Note: the above article I get from old literature but I forget to write the source. I also ever try to use the formula but not working smooth because use simple tools that I made by myself.

Result of Chrome Plating or Chrome Coating and Product Applied

The product variety can be as on the picture below:

1. Dull White Color Chrome Plating

The process of chrome plating coloring is just the setting in variety of voltage and ampere of electric  current and additive substance to make bright or smooth on coloring deposit.

Dull White Color Chrome Plating

2. Bright White Chrome Plating

Bright Chrome Plating

3. Gold Color Chrome Plating

Gold Color Chrome Plating

 

Gold Color Chrome Plating

4. Dull Black Color Chrome Plating

Dull Black Chrome Plating

5. Bright Black Chrome Plating

There are two different tipe of black chrome color from the chrome plating process, there are trivalen chrome plating process and hexavalent chrome plating process. Through trivalent chrome plating just can result semi black dark color, but this product have advantage of more stand to corrode. See black and color chromium deposit.

Hexavalent chrome or Cr (IV) plating process can result true dark deposit color, very dark, smooth and non reflective. Hexavalent chrome is not good for goods that purpose to stand in corrosive environment because the layer is not strong enough stick to the surface layer.

Bright Black Chrome Plating

Find of Bright Chrome Plating Service Company:

Example of Hard Chrome Plating:

Hard chrome applied on industry usually in their hydraulic shaft, this hydraulic need maintenance in certain period time need to coating again to repair the surface coating and adjust the hydraulic clearance.

Hard Chrome on Hydraulic Shaft

Beside on hydraulic shaft, industrial uses also apply hard chrome on rolls use for certain uses like in transfer material in production process.

Hard Chrome in Rolls

Hard chrome vanadium usually apply as coating on tools, this tool need hard surface in order not easily scratch when use to tight of open bolt from equipment.

Chrome Vanadium on Tools