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Plating
Plating usually describes a
process of metal finishing that deposits a metallic coating onto some form of
substrate. Plating is done to protect, beautify, increase corrosion or wear
resistance, affect conductivity of heat or electricity and or solderability of an
item. For our purposes, plating can be generally described by two different
processes, electroplating and electroless deposition. Electroless
plating involves the use of an aqueous solution containing metallic ions that is designed
to deposit the metal onto a substrate through autocatalytic reduction of the metallic ions
in the solution. Electroplating is a process where a
metal in solution is deposited onto an electrode that is negatively charged relative to
the solution. The item being plated can be referred to as the cathode. The solution
is charged through the use of an anode. Since the metal in solution is in ionic
form and contains a positive charge, it migrates toward the negatively charged
cathode. Once the metallic ion has reached the cathode it picks up the electrons and
is deposited onto the cathode (item being plated). The metallic coating accumulates
one atom at at time. Faraday's law states that for each Faraday of
electricity (96,5000 Coulombs of electrons), one gram of metal will be deposited on the
cathode. The plating industry uses Amperes as the measure of current flowing through
the system. One Ampere = 1 Coulomb of electrons for 1 second therefore it is
possible to determine the amount of metal deposited onto the cathode by factoring the
Amperes by the amount of time the current is flowing.
It is important to note
that the actual amount of metal deposited by the system is a product of Time, Current, and
bath efficiency. Since bath efficiency can range from less than 10% to more than
90%, it is important to understand the chemistry of the bath to monitor it's efficiency.
There are many factors that affect the properties of the deposit. A few of
the main factors are; Current density, which is the ratio of the system amperage
over the unit area of the anode or cathode. The temperature of the solution.
The pH of the solution. The concentration of metallic ions. Relative movement
of the solution and cathode.
In the future we will be building on the information base on this subject. We plan
to have hyperlinks from various key-words in this section to other sections for more
detail. Please Check Back Again Soon!
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Fundamentals of Plating Index
Plating With Gold
Physical Properties of Gold
| Atomic Number: |
79 |
| Atomic Weight: |
196.97 |
| Density: |
19.3 grams per cubic centimeter |
| Melting Point: |
1063 C |
| Boiling Point: |
2970 C |
| Thermal Conductivity: |
0.71 cgs units(20 C |
| Chemically Resistant to: |
Sulfuric acid (100 C), fuming sulfuric acid, persulfuric acid,
fuming nitric acid, 30% hydrochloric acid, perchloric acid, hydriodic acid, phosphoric
acid, acetic acid, tartaric acid, citric acid, selenic acid |
| Chemically Attacked by: |
Sodium and potassium cyanide plus oxygen, aqua regia,
chlorine, chlorine water, bromine and iodine in alcohol, selenic acid (+230C) |
Because of it’s
unique physical properties and lasting beautiful color gold has always been one of
man’s favorite elements. Since the beginning of recorded history gold has served as
an art medium and a symbol for wealth, eternity, the Sun, life, love and many other
desirable parts of the human experience. Aside from the psychological, metaphysical, and
religious appeal of gold it has certain physical properties that make it a desired medium.
From the ancient goldsmith to today’s scientist, gold is unique in is use.
At Gold Plating Services we provide
metal finishing and gold plating
for many different customers for many different reasons. Our customers have different
reasons for having gold applied to their items. We specialize in plating a 24Karat gold to
a specific MIL-Spec. (MIL-G-45204-C). Plating gold to this specification insures that the
final product will meet strict purity, thickness, and hardness standards. This
specification also mandates other factors such as undercoating, adhesion and
solderability. The specification also references other MIL and ASTM standards and
verification tests. We apply Mil-Spec plating to items for the aircraft, medical
instrumentation industry, and electronics industry. In some cases we are applying a 24K
gold plate to various grades of stainless steel and in others, we are plating onto copper
or brass alloys. In the future we will be
building on the information base on this subject. We plan to have hyperlinks from
various key-words in this section to other sections for more detail. Please Check
Back Again Soon!
Back to
Fundamentals of Plating Index
Plating Onto
Common Metals
We will be continuously adding to this
information base on methods of metal finishing and plating onto different types of substrate. In our
gold plating business we plate onto many different types of metal surfaces. One of
our clients has us gold plate coins struck in different substrates. A good example of the
type of gold plated coins is the 2000 Presidential Election
Coin. These coins are struck in a bronze copper alloy. When plating gold
onto any copper alloy, such as bronze, we normally plate with a bright nickel prior to
gold plating the coin. There are two reasons for this nickel plate. One
reason is to provide a diffusion barrier between the copper alloy and the gold plated
coin. This is important because over time, copper can corrode and diffuse through
the gold, changing the appearance of the gold. The second reason for the nickel
plate is to enhance the brightness of the finish. A mirror bright nickel plate will
give a high level of luster to the gold plated finish. We also do selective gold
plating onto coins. When doing selective gold plating onto coins, (or anything else
for that matter), we usually mask the area that we don't want to gold plate and then gold
plate the coin normally. The trick in doing selective gold plating coins is to apply
the mask in a manner that provides as much detail as possible. An example of selective gold plating on a coin is shown on our Golden Gifts
Trading Post. Selective gold plating onto coins has been very popular with the U.S.
Mint's State Quarters program. We are working with a major mint who has developed an
oversized States Quarters. We are offering these gold
plated, State Quarter replicas on our Golden Gifts Trading Post. They are
available in two grades. A bright un-circulated-circulated, 24K gold plated or German
silver (nickel) or LE Proof. Limited Edition Proof. The "LE Proofs"
are double struck in 1 oz .999 sliver and are also available in a 24K gold plate.
Scientific,
Technical and Special Purpose Gold Plating
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Is gold plating right for your project?
We get a large
number of inquires relating to the applicability of gold plating for
many different purposes. The gold plating services we provide fall
into three general categories. The type of plating process we use
depends on the customer's specific requirements.
Many times the customer requirements are a combination of the
following types of plating.
If you are
wondering if gold plating may be right for your needs you may want to
refer to the information that follows chronicling clients we serve that
have special needs. If you
need more information on the properties of different types of gold plate
please feel free to e-mail our technical with your questions.
terry@goldplating.com
1.
Decorative
The largest number of inquires for gold plating we receive
are for decorative purposes. While
there are other metals that have the same general appearance as gold,
they usually don’t offer the same corrosion resistance and combination
of physical properties as gold plating.
Gold plating is also very economical as a decorative finish when
compared to the other options. This
is especially true when you consider that much of the cost of providing
a decorative electroplated finish is incurred in the preparation of the
surface prior to the final finish.
An excellent example of this is in jewelry restoration.
The antique copper bracelet we restored, ( http://www.goldplating.com/Bracelet.htm
), required hours of
tedious labor to prepare the braclet for plating, this is where most of
the cost was incurred. The
actual value of the gold we applied was just a few dollars.
However, as far as the owner was concerned it turned a piece of
useless jewelry into a valuable heirloom that will be passed on for
generations. Generally
speaking, the cost of decorative gold plating is around $1.00 per square
inch (.2µm to .5µm thick). This
would not include any unusual finishing, restoration, special handling
or pretreatment. Of course
the price also is dependant on other factors such as quantity, size and
special tooling that may be required.
Many people are rightly concerned about the softness of 24K
gold for decorative applications. We
recognize the limitations of all electrodeposited finishes and strive to
give the customer the best information possible for making a choice that
is the most suitable for their purposes.
There have been many times when we have indicated that gold
plating is not appropriate for a particular purpose and have helped the
customer decide on a different choice.
For decorative gold applications, we normally recommend a cobalt
hardened 24 karat gold. This
gold is a 99.7% pure gold, is extremely corrosion resistant, and is
almost three times as hard as the pure gold we use for medical,
electronic and other applications where hardness isn’t required and
purity of deposit is.
2.
Corrosion resistance
Because of the relative low cost and high resistance to many
corrosive environments, we provide a great deal of gold plating that has
the primary purpose of providing corrosion resistance to a substrate
that otherwise would quickly corrode, such as copper.
This need arises quite often because the desirable electrical
properties of copper is quickly diminished by the reactive nature of the
copper surface. While gold
is not as conductive as most copper
or silver, gold does provide much better resistance to corrosion than either
metal. Hence, we often
provide a gold plate over a copper or silver substrate.
An excellent example of using gold plating as a corrosion
resistant barrier for a copper substrate is found on our home page.
The RF load coil shown is a key component of an inductively
coupled plasma mass spectrometer, (ICP-MS).
These coils operate in an extremely harsh environment under high
temperatures, and have to withstand high frequency electrical current
without significant degradation of the surface.
The scientist who developed, and patented these high performance,
corrosion resistant coils had tried different combinations of transition
elements before settling on this particular process which involves
the application of an extremely heavy pure gold electroplate over
a copper substrate with a transition element diffusion barrier.
For a better look at these coils and a more information on their
performance specifications you can visit http://www.noblecoil.com/.
Even a bright, hard gold is somewhat porous; therefore when the
gold is applied over a substrate that poses the possibility of diffusing
through the gold, such as silver or a copper alloy, we normally suggest
a “diffusion barrier” such as nickel.
This will help insure that the substrate is protected against the
environment. We provide
gold plating services for some high-energy research laboratories that
specify the deposit must not be magnetic.
Since most nickel deposits are magnetic to varying degrees this
precludes the use of nickel as a diffusion barrier.
In this case we usually recommend increasing the thickness of the
gold plate to a level that prevents significant diffusion under most conditions, 2µm is generally
sufficient.
3.
To provide physical properties unique to gold such as reflectivity
or conductivity.
We have many research and development labs contact us about gold
plating for their projects because of some of the other known properties
of gold plating. One such
contact was a company developing a medical laser. The gold plating they required was for excellent reflection throughout the spectrum from visible through near-IR (e.g. up to 820nM and specifically 808nm, the most important wavelength for Nd:YAG lasers).
They indicated measurements on our plating in excess of 97% reflection throughout this spectrum.
Since they were looking for a reflector that works in the 808nm
range, gold was the perfect choice for their project.
The reflectors were a 316 stainless steel, we provided 1µm of hardened gold applied directly to the polished surface.
We have another client that produces equipment that utilizes a
component that operates in such a harsh environment that nothing they
had tried would prevent the item from literally burning up in just a few
hours. Our technical staff
worked with their development engineers to find a solution that utilized
a pure nickel substrate followed by a heavy (2µm+) pure rhodium plate
with 5µm of a 999+% gold deposit.
The components produced utilizing this very specialized process
have preformed for months of extreme, continuous testing.
Because of its inert chemical properties, versatility of
application and relatively low cost, electroplating of gold has proven
to be the answer to many engineering and technical problems.
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Frequently
Asked Questions
(Q) .. Is it really possible to make money with a portable gold plating business?
(A)
.. Absolutely, we have many customers that
started their portable gold plating business on a part time basis with little
more than a cell phone and the components that initially came in their
original electroplating kit. With a service oriented attitude and
some persistent work, they have grown
it into an excellent income. Others have kept is as a part time "extra
income" business only plating a few cars a month. Because there is
virtually no fixed overhead, it works perfectly as a part time business. Follow
this link for more information on making money with a gold plating business.
(Q)
.. I work in an auto auction & am in a
parking lot every day & inspecting emblems. I honestly don't know a gold
plated emblem from a gold colored plastic yet. I've seen several that are
darkened and others that look as if they have black bubbles through out.
Would these be simply plastic or poorly applied gold? (A)
.. Probably
both. Most automotive emblems are plastic and most of the emblems that
look gold, (in good or bad condition), are plastic emblems that have
been gold plated. The reason that the bad looking gold looks bad is
most likely the result of being plated with a "short cut" method
of gold plating or they were plated by someone that wasn't concerned about
the quality of their work. We are trying to head off this image in our
industry by promoting high quality workmanship, not just going for the fast
buck now. We do this by only promoting the most durable process of
automotive gold plating, i.e. chrome removal and applying the gold heavy enough to insure
corrosion protection to the underlying nickel. Any gold plated
layer is relatively thin and somewhat porous. If the gold layer isn't
thick enough to seal off the underlying nickel plate then corrosive
environmental conditions can corrode the nickel plate. When the nickel
plate corrodes, it first forms tiny black pits. The black pits
develop into small mounds that look something like a miniature volcano when
magnified. These mounds are caused by the corroded nickel expanding under the surface.
From a distance this nickel corrosion can appear as a general darkening of the emblem.
When the nickel gets to this point, the emblem most likely needs to be
re-plated with nickel and is probably not worth saving. At Gold Plating Services, we
have always offered a lifetime warranty on our automotive gold plating.
We guarantee that the gold we apply plate won't peel, flake, or corrode for
the life of the car. We
promote a process that allows this type of warranty. By the way, there
are a few vinyl automotive "emblems" (I call them decals) that
are suppose to look like gold, they are soft and will indent if you
push on them with your thumbnail.
(Q)
.. I've heard that the thickener used to
convert liquid brush plating gold to a gel reduces the amount of actual gold solution I
receive by up to 1/3. Does your gold thickener add to the volume of gold?
(A)
.. NO, the thickener we use is a very fine
powder. The amount required to thicken an 8oz jar of gold actually increases the total
volume of the solution by less than 2%. We compensate for the added volume by slightly
overfilling the jar. When you buy the solution you are actually buying the pre-thickened
volume. We do, however have some customers that prefer to buy the solution as a liquid and
the thickener on the side. They then add the thickener to suit their personal preference.
(Q)
.. Why is aluminum so difficult to plate?
(A)
.. Aluminum is a very reactive metal.
After being polished or cleaned the surface oxidizes within seconds of coming
into contact with the air. The resulting thin layer of aluminum oxide is very inert,
coherent, and protective and cannot be reduced (returned to the pre-oxidized state)
electrolytically. The oxide layer cannot be plated onto. One typical method used to plate
onto aluminum involves removing the oxide layer using a strong alkaline solution which
simultaneously replaces the oxide film with a layer of zinc (known as zincating). The
zincated part can then be plated with an electroless nickel or alkaline copper solution.
The part can then be plated normally. The use of the extremely caustic zincate solution
and hot dip electroless nickel solution makes plating onto aluminum impractical for most
portable platers using standard electroplating kits. Many larger chrome shops can economically plate a heavy coat of hot-dip
decorative nickel onto aluminum. This will produce a very hard mirror bright surface that
then easily be gold plated. While it is possible to plate onto aluminum using a portable
system, the process is not cost effective and the durability of the resulting finish is
generally not sufficient for long term service. When we have a customer that wants an
aluminum part gold plated we always recommend a procedure that involves a hot-dip nickel
layer.
(Q)
.. Would
your machines work to repair chrome for hotrod/muscle car enthusiasts? Would the
pieces need to be completely stripped down or could chrome be applied in
these scratched/"injured" areas?
(A)
.. Our system will repair chrome as well or better than any portable system
on the market. However, I like to give people an honest answer to the
chrome repair question. You need to understand that chrome is normally
plated over a heavy, hot dip immersion nickel that produces a lot of thickness
relative to the chrome plate. The heavy nickel plate is plated over a
heavy copper plate. Therefore, offering a "chrome plate repair"
without being able to also repair the underlying copper and nickel is a little
like trying to fix a dent in a fender by simply applying a thin layer of paint.
While it is possible to sand out the ding, plate with copper, polish, plate with
nickel, polish and then plate with chrome this repair would require a lot of
time and a high level of craftsmanship, and almost never would be worth the
effort. This is especially true in light of the fact that a large chrome
shop will straighten, strip and completely re-plate an entire bumper for a
couple of hundred dollars. There are well established, large chrome
plating businesses that have invested millions of dollars in chrome plating
equipment. These companies such as Ogden
Chrome Plating, provide an extremely high level of service for a relatively
low price. It is our opinion that it is not smart for a person with a
portable plating system or a home based (bucket) chrome plating system to
compete with these well established companies. This is epically true when
the environmental regulations and procedures for disposal of rinse water and
spent solutions is taken into account. There are far more profitable ways to utilize a
portable gold plating system. In fact, I have never heard of anyone that
has made a profit offering portable automotive chrome repair.
(Q)
.. How can I tell if a conductive surface is
chrome, aluminum, or stainless steel?
(A)
.. Most silver colored, metallic (conductive),
surfaces encountered in everyday use are either chrome, stainless steel, aluminum, nickel,
zinc or silver.
If you are faced with a surface and don't know what it is. By using our portable plating
system, you can determine which of the above four it is by grounding the part and touching
the surface with your chrome stripping wand. If it is chrome plated there will be a
distinct yellowing of the chrome stripping solution. Careful analysis of the surface after
you have worked on it with the chrome wand will reveal a slightly darker, bright metallic
surface, (the nickel) as opposed to the chrome that has more of a blue tint. If the item
is stainless steel, you should be able to detect some light, bubbling action where the
wand is in contact with the surface. The stripping process won't have any affect on the
appearance of the surface, however the solution may develop a light purple tint. An
aluminum part may initially react like stainless steel. The chrome stripping solution will
lightly attack the surface of the aluminum, when you have moved the wand away from the
surface there may still be some light bubbling where the solution was left on the part.
After rinsing, the area that you tried to strip may be slightly milky white and with less
luster. Normal polishing with metal polish will return the surface to its previous
condition. Since polishing may be required on aluminum items, it is recommended that you
try a very small area on items that could be aluminum. Silver surfaces will immediately
turn black when you try to strip them with the chrome stripper. Don't worry, the nickel
activator will remove the smut. Zinc parts won't have any reaction to the stripper, but
the nickel activator will attack the zinc surface even without having the common applied.
If you then try to gold plate a zinc part using our normal gold solution, the part will
turn black.
(Q) .. Why do I need to use a nickel strike on
stainless steel?
(A) ..
Stainless steel, is a family of steel alloys that contain, among other things,
15% to 20% chromium. The chromium is a little like aluminum in that it forms a thin, self-healing layer of
chromium oxide. The chromium oxide is inert and therefore highly corrosion resistant and
difficult to plate onto. Fortunately, unlike aluminum oxide, the chromium oxide can be
chemically reduced using an acid solution. If the acid solution contains nickel, such as
the Woods Nickel Strike that comes in our electroplating kits, the reduced chrome can then be simultaneously plated with the
nickel in the strike. The part can then be activated and plated normally. Remember that a
key step in our stainless procedure is to abrasively remove the all of the oxide layer
possible prior to the nickel strike step. Since we have had so many questions on the
stainless procedure, I have revisited our published stainless procedure and amended it. I
have taken out the nickel prep step, which is only necessary under extremely oily
conditions. Click here for the stainless steel procedure
(Q)
.. Does an automobile emblem
have to be removed before it can be gold plated.
(A)
.. Not usually,
our electroplating kit utilizes a unique process has been developed to allow the technician to leave the emblem on the
car in almost every case. The plating solutions will not affect most new car finishes. Our
training will teach you how you can tell if there could be a risk of having a problem with
leaving an emblem on the vehicle. Being able to leave the emblems on the vehicle provides
a great advantage for the on-site plater. Imagine the cost of removing the emblems,
sending them to a plating company and then having to re-install the plated
emblems, and then having to re-install the plated emblems. You
can see exactly how an emblem is plated while on the car by following this
link. 
(Q)
.. How long will the gold last ?
(A)
.. 24 Karat gold will never
corrode under normal conditions. The plating that is applied with our system is the same as any other 24 karat gold
electroplate, no more or less. While 24 Karat gold will never corrode under
normal conditions and if applied
correctly should never peel, flake or fade it is very soft and needs to have proper care
to insure maximum life.
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