Hard Chrome electro plating, sri perfect electro platers, coimbatore

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SRI PERFECT ELECTRO PLATERS
Hard CHROME ELECTRO PLATING PROCESS
33, Electro Plating Industrial Estate,
Codia Park, Kurumbapalayam,
Coimbatore-641107
E Mail: [email protected]
Phone No: +91 98433 19320
HARD CHROME ELECTRO PLATING, SRI PERFECT ELECTRO PLATERS, COIMBATORE
SRI PERFECT ELECTRO PLATERS
Company Name
: Sri Perfect Electro Platers
Proprietor
: C.Shanmugam (Mani)
Address: Site No
:33, Electro Plating Industrial Estate,
Codia Park, Kurumbapalayam,
Coimbatore-641107
Phone Number
: +91 98433 19320
Email
: [email protected]
Website
: sriperfectelectroplaters.hpage.com
Certified by Anna University, Chennai
as a Centre for Environmental Studies
Company Belongs to : Hard Chrome Plating
Operating from Since :1998
Working process
: Job works alone. Not any manufacturing.
Clients
:Roots, L&T and more small scale companies
Some Acids using
: H2CrO4 -- "hexavalent chromium", HCL etc.
Typical chromed parts would be: Automotive valve stems, piston
rings, shock rods, Mac Pherson struts, the bores of diesel and aircraft
engine cylinders, and hydraulic shafts.
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+91 98433 19320
Introduction Electroplating:
Electroplating is a plating process in which metal ions in a solution are moved by an electric
field to coat an electrode. The process uses electrical current to reduce cations of a desired
material from a solution and coat a conductive object with a thin layer of the material, such as a
metal. Electroplating is primarily used for depositing a layer of material to bestow a desired
property to a surface that otherwise lacks that property. Another application uses electroplating
to build up thickness on undersized parts.
Some Additional Informations:
Although it is not confirmed, the Parthian Battery may have been the first system used for
electroplating.Modern electrochemistry was invented by Italian chemist. Luigi V. Brugnatelli in
1805. Brugnatelli used his colleague Alessandro Volta's invention of five years earlier, the
voltaic pile, to facilitate the first electrodeposition. Brugnatelli's inventions were suppressed by
the French Academy of Sciences and did not become used in general industry for the following
thirty years.
Process:
The part to be plated is the cathode of the circuit. In one technique, the anode is made of the
metal to be plated on the part. Both components are immersed in a solution called an electrolyte
containing one or more dissolved metal salts as well as other ions that permit the flow of
electricity. A power supply supplies a direct current to the anode, oxidizing the metal atoms that
comprise it and allowing them to dissolve in the solution. At the cathode, the dissolved metal
ions in the electrolyte solution are reduced at the interface between the solution and the cathode,
such that they "plate out" onto the cathode. The rate at which the anode is dissolved is equal to
the rate at which the cathode is plated, vis-a-vis the current flowing through the circuit. In this
manner, the ions in the electrolyte bath are continuously replenished by the anode.
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Detail Process of Plating:
The anode and cathode in the electroplating cell are both connected to an external supply of
direct current — a battery or, more commonly, a rectifier. The anode is connected to the positive
terminal of the supply, and the cathode (article to be plated) is connected to the negative
terminal. When the external power supply is switched on, the metal at the anode is oxidized from
the zero valence state to form cations with a positive charge. These cations associate with the
anions in the solution. The cations are reduced at the cathode to deposit in the metallic, zero
valence state. For example, in an acid solution, copper is oxidized at the anode to Cu2+ by losing
two electrons. The Cu2+ associates with the anion SO42- in
the solution to form copper sulfate. At the cathode, the Cu2+
is reduced to metallic copper by gaining two electrons. The
result is the effective transfer of copper from the anode
source to a plate covering the cathode.
The plating is most commonly a single metallic element, not
an alloy. However, some alloys can be electrodeposited,
notably brass and solder.
Many plating baths include cyanides of other metals (e.g.,
potassium cyanide) in addition to cyanides of the metal to be
deposited. These free cyanides facilitate anode corrosion, help to maintain a constant metal ion
level and contribute to conductivity. Additionally, non-metal chemicals such as carbonates and
phosphates may be added to increase conductivity.
When plating is not desired on certain areas of the substrate, stop-offs are applied to prevent the
bath from coming in contact with the substrate. Typical stop-offs include tape, foil, lacquers, and
waxes.
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Hard Chrome Plating
Hard chromium plating is produced by Electrodeposition in a solution of chromic acid. It is also
known as industrial, functional or engineering
chromium plating and is very different from
decorative chromium plating.
Hard chromium plating is commonly used to
restore original dimensions to worn surfaces of
large crank-shafts for diesel, gas engines and
compressors. Hard chrome also finds use in the
repair of impaired printing and paper making roll
bearing journals.
A tank that contains CHROME
Hard chromium deposits are intended primarily to increase service life of functional parts by
increasing their resistance to wear, abrasion, heat and corrosion. Plus hard chrome is used to
restore dimensions of undersized parts.
Chrome:
Chrome is slang for Chromium, one of the 92 naturally occurring chemical elements. Chrome is
a metal, but it is not useful as a solid, pure substance. Things are never made of solid chrome.
Rather, when you hear that something is chrome, what is really meant is that there is a thin layer
of chrome, a plating of chrome, on the object (the bulk of the object usually being steel, but
occasionally aluminum, brass, copper, plastic, or stainless steel).
A cause of occasional confusion is the fact that people may tend to describe any shiny finish as
"chrome" even when it really has nothing to do with chromium. For example, brightly polished
aluminum motorcycle parts, electro polished stainless steel boat rigging, vacuum metallized
balloons and helmets, shiny painted wheels, and nickel plated oven racks are sometimes called
'chrome' by the lay person.
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Indeed it's not always easy to tell chrome plating from
other finishes if the parts are not side by side. When a
decorative chrome electroplated finish sits right next
to another bright finish, however, the other finish
usually won't compare very favorably :-)
Chrome plating is more reflective (brighter), bluer
(less pale, grayish, or yellowish), and more specular
(the reflection is deeper, less distorted, more like a
mirror) than other finishes. Put one end of a yardstick
against a bright finish, and see how many inches of
numbers you can clearly read in the reflection -- you
can clearly see the clouds in the sky reflected in
chrome plating. And there's a hard to define "glint" to
top quality chrome plating that nothing else has.
Temprature control will be done by this.
What is the Process of Hard Chrome plating:
A component to be chrome plated will generally go through these different stages:

degreasing to remove heavy soiling;

manual cleaning to remove all residual traces of dirt and surface impurities;

various pretreatments depending on the substrate;

placement into the chrome plating vat, where it is allowed to warm to solution
temperature; and

application of plating current, under which the component is left for the required time to
attain thickness.
There are many variations to this process depending on the type of substrate being plated upon.
Different etching solutions are used for different substrates. Hydrochloric, hydrofluoric, and
sulfuric acids can be used. Ferric chloride is also popular for the etching of Nimonic alloys.
Sometimes the component will enter the chrome plating vat electrically live. Sometimes the
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component will have a conforming anode either made from lead/tin or platinized titanium. A
typical hard chrome vat will plate at about 25 micrometres (0.00098 in) per hour.
Various Linishing and Buffing processes are used in preparing components for decorative
chrome plating. The overall appearance of decorative chrome plating is only as good as the
preparation of the component.
The chrome plating chemicals are very toxic. Disposal of chemicals is regulated in most
countries.
What's the difference between "Chrome Plating", "Chrome Electroplating", "Chrome
Dipping", "Chroming", etc.?
Nothing. Chrome is always applied by electroplating, it is never melted onto parts in the fashion
of chocolate on strawberries, or applied in any other way than by electroplating.
Is all chrome plating about the same, then?
Not quite. There are two different general applications for chrome plating: "hard chrome plating"
(sometimes called 'engineering chrome plating') and "decorative chrome plating" (sometimes
called 'nickel-chrome plating').
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Some parts that are to be Hard Chrome plated(Parts of borewell Pumps, Milling Machines, & others
Hard Chrome Plating
Most people would not be very familiar with hard chrome plating. Hard chrome plating is
chrome plating that has been applied as a fairly heavy coating (usually measured in thousandths
of an inch) for wear resistance, lubricity, oil retention, and other 'wear' purposes.
Some examples would be hydraulic cylinder rods, rollers, piston rings, mold surfaces, thread
guides, gun bores, etc. 'Hard chrome' is not really harder than other chrome plating, it is called
hard chromium because it is thick enough that a hardness measurement can be performed on it,
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whereas decorative chrome plating is only millionths of an inch
thick and will break like an eggshell if a hardness test is
conducted, so its hardness can't really be measured directly.
Hard chrome plating is almost always applied to items that are
made of steel, usually hardened steel.
It is metallic in appearance, and can be shiny, but is not
necessarily decorative. Hard chrome plating is not a finish that
you would want on a wheel or bumper.
A Small part of a Big machine that need to be Chrome plate
There are variations even within hard chrome plating, with some of the coatings optimized to be
especially porous for oil retention, others "thin dense chrome", and so on.
Many shops who do hard chrome plating do no other kind of plating at all, because their business
is designed to serve only engineered, wear-type, needs. If a shop says they do 'hard chrome only',
they have no service that most consumers would be interested in. Follow the link for a list of
some shops that offer hard chrome plating.
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Decorative Chrome Plating
Decorative chrome plating is sometimes called nickel-chrome plating because it always involves
electroplating nickel onto the object before plating the chrome (it sometimes also involves
electroplating copper onto the object before the nickel, too). The nickel plating provides the
smoothness, much of the corrosion resistance, and most of the reflectivity. The chrome plating is
exceptionally thin, measured in millionths of an inch rather than in thousandths.
When you look at a decorative chrome plated surface, such as a chrome plated wheel or truck
bumper, most of what you are seeing is actually the effects of the nickel plating.
The chrome adds a bluish cast (compared to the somewhat yellowish cast of nickel), protects the
nickel against tarnish, minimizes scratching, and symbiotically contributes to corrosion
resistance.
But the point is, without the brilliant leveled nickel undercoating, you would not have a
reflective, decorative surface.
By the way, there is no such thing as "decrotif chrome plating". That is just a misspelling of
'decorative'.
Thicknesses
Hard chromium is deposited in thicknesses ranging from one to twenty thousandths and in
certain applications to much greater thicknesses. Decorative coatings of chrome rarely exceed
.05 mil.
With certain exceptions, hard chromium is applied directly to the base material. Decorative
chrome is applied over undercoats of nickel, copper and nickel and can be then polished or used
as plated.
Hard chromium plating is used for restoring mis-machined or worn surfaces. However, since
1970, in some cases, electro-deposition of hard chrome has been replaced by thermal spraying
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and plasma coating since it can be applied more quickly and with better control over the
coating's thickness.
In these applications, coating thicknesses range between five and fifty thousandths and the
excellent wear qualities and low coefficient of friction of chromium are highly advantageous.
However, care must be taken not to plate in fillet areas as a precaution against fatigue failures.
"Show chrome", "Triple Chrome Plating", "Double Nickel-Chrome"
"Show chrome" probably means chrome that is good enough to be on a winning entry in a car
show. Although most OEMs rely on the "self-leveling" property of nickel plating to give
sufficient reflectivity to roughly polished steel, chrome-lovers believe that the key to "show
chrome" is to copper plate the item first and then buff the copper to a full luster before starting
the nickel plating.
Whether you start with bare steel or buffed copper, at least two layers of plating follow -- a layer
of nickel and a layer of chrome. But high quality plating requires either very thick nickel or a
minimum of two layers of nickel.
Salespeople are always looking for advantage, and they will use any good-sounding terms they
can get away with! There are no laws that define what triple chrome plating actually means, so
salespeople will be prone to call their service "triple chrome plating" if there are a total of 3
layers of any kind of plating, or "quadruple chrome plating" if there are 4. So those terms mean
little.
By the way, tri-chrome is not an abbreviation for triple chrome, and hex chrome does not mean
six layers. But more on that later . . .
The most important issue for durable chrome plating for outdoor exposure such as on a vehicle is
that it should have at least two layers of nickel plating before the chrome: namely semi-bright
nickel followed by bright nickel. The reason for this involves galvanic corrosion issues. The
bright nickel is anodic to the semi-bright nickel, and sacrificially protects it, spreading the
corrosion forces laterally instead of allowing them to penetrate through to the steel. OEMs
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demand very close control of this factor, and there is a test (the Chrysler developed STEP test)
which large shops run daily to insure the right potentials. Careful control of this issue is probably
the principal reason that today's chrome plating greatly outlasts the chrome plating of earlier
times. If a restoration shop offers only single layer nickel plating, they must apply it really really
heavy if corrosion resistance is to be guaranteed.
Experts argue whether copper plating provides any additional corrosion resistance at all, but with
or without copper plating, chrome on top of a single thin layer of nickel will not hold up to the
severe exposure of a vehicle! Industry professionals call the two layers of nickel "duplex nickel
plating", and that would be a much better term to use than "triple chrome" and such.
Why should we go for hard chromium plating?
The decision to employ hard chromium plating would be dictated by the following needs and
requirements:
1. The inherent hardness and wear resistance of electro-deposited chromium.
2. Thickness of chromium required.
3. Shape, size, construction and material the part is made from.
4. Masking requirements for areas not to be plated.
5. Dimensional requirements and if additional mechanical finishing will be needed.
Hardness of chromium electro-deposits is a function of plating conditions. Generally, chrome
plated in the bright condition is optimally hard. Bright chromium deposits from conventional
baths have a Vickers hardness of 900 to 1000; those from mixed catalyst baths have hardnesses
of 1000 to 1100 or higher.
Color Chrome
With the exception of Black Chrome plating, there is no such thing as colored chrome. Rather,
those colored coatings are translucent paints applied over a layer of tiny aluminum flakes, and
should be called "chrome-look paint"; more on this later.
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Some "black chrome" is probably "chrome-look paint", but real black chrome plating is achieved
with a contaminant that turns the metal smoky grey or fully black. Black chrome can be a
decorative finish for automobile parts, or a matte finish for non reflective coatings on
microscopes and optical equipment, or a great coating for solar collectors. We have an excellent
podcast interview about black chrome.
Restoration Work
Chrome plating is hardly a matter of dipping an article into a tank, it is a long involved process
that often starts with tedious polishing and buffing, then cleaning and acid dipping, zincating (if
the part is aluminum), and copper plating.
For top reflectivity "Show Chrome", this will be followed by buffing of the copper for perfect
smoothness, cleaning and acid dipping again, and plating more copper, then two or three
different types of nickel plating, all before the chrome plating is done. Rinsing is required
between every step.
When an item needs "rechroming", understand what is really involved: stripping the chrome,
stripping the nickel (and the copper if applicable), then polishing out all of the scratches and
blemishes (they can't be plated over and any scratches will show after plating), then plating with
copper and "mush buffing" to squash copper into any tiny pits, then starting the whole process
described above.
Unfortunately, simply replating an old piece may cost several times what a replacement would
cost. It's the old story of labor cost. The new item requires far less prep work, and an operator or
machine can handle dozens of identical parts at the same time whereas a mix of old parts cannot
be processed simultaneously, but must be processed one item at a time. If a plater has to spend a
whole day on your parts, don't expect it to cost less than what a plumber or mechanic would
charge you for a day of their time.
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Uniformity
Hard chromium is laid down by an electroplating process. Compared with other electroplating
processes, the hard chrome plating baths have a slow or poor plating ability and this ability is
very dependent on plating bath chemistry. Plating can be good over a period of time but if the
bath composition shifts, it will markedly change the plating rate and the quality of plating.
Although the throwing power of the process is slow, the little bit of hard chrome that migrates
into a precision bored hole or an internal thread can be very difficult to remove. Such holes
should be closed off with a Teflon plug. All plugs should be removed before draining and
rinsing.
On single parts or short runs, you are dependent on the plating shop's past experience in getting a
uniform plating job. On long production runs, the plating shop can usually figure out with time
just what anode configuration will result in acceptable uniformity. There are three dimensional
computer programs that will simulate the electric field between the anode and the parts when
immersed in the plating solution. However, they do not simulate the convection and the
circulation of the plating solution between the anode and the part to be plated, so the results of
the computer models are imperfect. They will, however, markedly reduce the plating shop's
amount of experimentation.
A good simulation program is essential when evaluating a potential supplier of hard chrome
plating. Also, you should look for good record keeping of anode configuration vs. results for all
the parts the shop is running.
Residual Stress
All residual stress in your part must be under control before plating. You must do a stress relief
or the plating results will be variable. The density of porosity and microcracking and flaking in
service will all be affected. Residual stress is very difficult to quality control and your plating
shop will probably insist on a clause in the P.O. that lets them out of any performance
requirements if you provided parts having residual stress.
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Buffing Process:
Buffing may be required for some goods. Buffing will be done by electrical motor. It may be to
remove oil and grees that the material contain. Various kinds of Soaps are using in this process to
avoid depreciations during buffing. Buffing will be done after Plating also to get more shine.
Buffing machine
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Various size of Wheels that are using for buffing
Stripping
It seems inevitable that parts have to be stripped and replated. The stripping method will depend
on the substrate. Hydrochloric acid with inhibitors works for some substrates while deplating in
an alkaline solution performs for others.
In either case, high strength alloys can suffer hydrogen embrittlement and pitting can be a
problem. Early into a hard chrome plating contract it may be advisable to have the plating shop
plate and strip some parts to determine what is the best process for deplating, prior to any
production crisis.
Cleanliness
Cleanliness is essential to successful electroplating, since molecular layers of oil can prevent
adhesion of the coating. Cleaning processes include solvent cleaning, hot alkaline detergent
cleaning, electro-cleaning, and acid treatment etc.
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The most common industrial test for cleanliness is the water
break test, in which the surface is thoroughly rinsed and held
vertical. Hydrophobic contaminants such as oils cause the water
to bead and break up, allowing the water to drain rapidly.
Perfectly clean metal surfaces are hydrophilic and will retain an
unbroken sheet of water that does not bead up or drain off.
ASTM F22 describes a version of this test. This test does not
detect hydrophilic contaminants, but the electroplating process
can displace these easily since the solutions are water-based.
Surfactants such as soap reduce the sensitivity of the test and
must be thoroughly rinsed off. Lack of cleanliness will cause on
Re-work.
Regulations
Waste Tree powders using to clean
from oil and water
Electroplating was our nation's very first categorically regulated industry. So, what does
"categorically regulated" mean? It means that all of the waste products from this industry -- even
very dilute rinse water -- are, as a matter of law, regulated, even if the particular substance is so
dilute that it is actually harmless.
Mix the waste in with other waste, and the whole mass is by law hazardous waste (see EPA
'mixture rule'). Make another product from it and (with some exception) the product is hazardous
waste.
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Further Steps:
After all process the typical product will be given to the supplier. The information of finishing
will be informed by phone. Usual packaging will be done and some times even that is not
required.
After plating work, Grinding work will be done for that product. If it is not required (only for
specific materials) that will be taken for next step as per companies requirement.
Package mostly using news papers
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Machine that uses for Buffing long Products
25HP of Power
Conclusion
Hard chrome plating has proved itself to be a useful process to provide a long life, durable
bearing surface. Now a days Power off, Asid and other chemical cost and labor problem is a very
big issue of this job. However, in using this process, one must be very careful to insure the
substrate is properly prepared as to stress relief, surface finish and cleanliness.
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Hard Chrome electro plating, sri perfect electro platers, coimbatore

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