Tin plating applications include corrosion protection, to facilitate soldering, to improve anti-galling characteristics, and for use as a stop-off barrier in the nitriding of high-strength steels. Color is gray-white, and ranges from matte to bright in appearance depending on the process used. Tin deposits are soft and very ductile, however, are not suitable in low temperature applications.
MIL-T-10727 Tin Plating: Electrodeposited or Hot-Dipped (This cancelled spec is still in wide use.)
Electrodeposited. Reference ASTM B 545 - Standard Specification for Electro-deposited Coatings of Tin
ASTM B 545 Standard Specification for Electrodeposited Coatings of Tin
- C0.00032" (0.0004" for steel)
- D0.0006" (0.0008" for steel)
Tin should be not less than 99.5% pure except when alloyed for special purposes
An underplate of nickel at least 50μ" thick is required for tin coatings of 100μ" or less that will not be exposed to solder temperatures (especially ones that will function as a conductive surface).
To prevent zinc migration and poor solderability during service or storage, brass or other copper alloys containing more that 5% zinc must have a copper underplate layer of at least 100μ", or a nickel underplate layer of at least 50μ" (Barrier Layers).
Metal whiskers sometimes grow spontaneously from the surface of electrodeposited metals such as tin, cadmium, and zinc during a period that can vary from weeks to years. These whiskers are about 100μ " in diameter, can grow up to 3/8 inch long and can have a current carrying capacity of as much as 10 mA.A tin-lead plating that is extensively used for the prevention of whiskering has a nominal lead composition of 7.0±5 % by mass, the balance being tin.
AMS 2408 Tin Plating
Tolerance: +0.0002" unless otherwise specified
ABOUT CORROSION PROTECTION
Some corrosion may be expected from tin coatings exposed to outdoor environments. In normal indoor exposure, tin is protective on iron, steel, copper, and copper alloys.