Metal stamping guides and resources for designers, engineers and metal part buyers. Valuable information for anyone considering metal stampings in their manufacturing process.
Secondary Process --- Plating
Plating electrically or chemically applies a secondary metal to the surface of metal parts. Usually for corrosion resistance or electrical properties but also for cosmetic reasons.
The most common form of plating is electroplating. This is accomplished by dipping the part in an acid solution where an electrical current is passed through the part and a plate of the metal to be deposited. The negative charge is on the part and it attracts ions of the metal to be deposited which is connected to the positive charge.
Ions from the metal use for
plating are drawn from the
anode with the positive
charge toward the part
to be plated by the negative
charge on the part. They
then bond with the metal
in the part.
Electroless is a plating process which does not require electrical current. A chemical process is used with a catalytic reduction process of nickel ions in a solution and the subsequent deposition of metal. This results in exceptional corrosion resistance and high hardness.
The reduction of nickel metal ions and their deposition is driven by a chemical reducing agent in the solution. As long as the solution is evenly mixed the nickel ions can be applied uniformly in thickness all over the part. This process offers distinct advantages when plating irregularly shaped objects, holes, recesses, internal surfaces, valves or threaded parts. Advantages of electroless plating are:
Uniformity of the deposits
Much less hydrogen absorption as electrolytic nickel or hard chrome.
Deposits which provide a better barrier to corrosion
Deposits have smoother surface
Deposits can be plated with compressive stress
Application of oils is more uniform
Better solderability than electroplated material
Deposits are much harder
This just as in electroplating where opposite charges attract. The part is coated and is electrically charged, then is sprayed with a non-metallic powder that sticks to it. The object is then passed through an oven where the powder particles melt and stick to the part with a very smooth finish. Unlike painting processes the finish is very hard as well as the process not requiring volatile organic compounds and special environmental procedures.
This process for aluminum involves producing a very thin, invisible layer of the oxide on the surface, which protects it from corrosion. The oxide is a chemical combination of aluminum and oxygen. It can be in many different colors.
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