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ChemPosit Sn RD-51

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An Immersion Tin Plating bath for Copper, Tin/Lead and other Metals

ChemPosit Sn (RD-51) Immersion Tin plating bath plates a brilliant dense smooth Tin deposit onto various copper alloys, and other less noble metals, leaving a corrosion resistant surface that is highly solderable, even when the substrate was not. Since ChemPosit Sn (RD-51) deposits a brilliant finish, subsequent reflowing operations may be avoided. It is important to recognize that ChemPosit Sn (RD-51) is a chemical plating (rather than "electro-plating") bath. As a consequence, uniform plating can be expected on all surfaces (shape and size have no bearing on deposit quality).

ChemPosit Sn (RD-51) Immersion Tin plating baths operate more easily and are "poisoned" less readily than other Immersion Tin plating chemistries.

Precleaning: Parts to be plated should be free of soil and tarnish. Badly soiled parts should be precleaned in an alkaline cleaner, MicroClean CuLX (RD-68) is best for copper. Light finger printing and tarnish may be effectively removed by cleaning in Acid Prep. Any alkaline cleaner that is used should be followed by a thorough rinsing and at least a short immersion in Acid Prep to neutralize any alkaline residues.

Add 1-1/4 lbs of ChemPosit Sn (RD-51) to each gallon of hot water. No Hydrochloric Acid is required.

The product will become insoluble at temperatures of less than 110º F. When cooled, a white precipitate will form, which will readily redissolve on re-heating.

ChemPosit Sn (RD-51) will work at 120º - 170º . We recommend 160º F. Typically a bath used at 160º F may be left covered, with the heaters off overnight, and still be warm enough (above 120º F) to use first thing the next morning.

Minimum 5 minute immersion times are required in a new bath for corrosion protection. Increased deposition time will be required as the bath is consumed, or if the bath is used at less than 160º F.

Work agitation or other mechanical agitation is required to assure even plating in restricted areas, like holes. Do not use air agitation.

Tanks should be made of polypropylene or other plastics. Tanks made of fiberglass should not be used.

Note: Use only Carbate or Teflon coated heaters. Quartz or stainless steel heaters will be attacked.

Make up water loss due to evaporation to within 90% of original volume. Keep tin within concentration range, add salts or discard bath. The pH will be 1.8, do not reduce pH with HCl.

Thorough rinsing is required. Best results are obtained using a hot rinse followed by an overflow cold rinse. Prolonged cold water overflow rinsing is adequate for metal parts only.

Coverage will occur within the first minute. We recommend at least a 5 minute immersion for excellent salt spray corrosion resistance. Plating will continue at a decreasing rate for 20 minutes, to a maximum of 45-50 microinches (1.1 – 1.2 microns).


Product contains Thiourea. Consult Material Safety Data Sheet for detailed Safety information.

Spent solutions of ChemPosit Sn (RD-51) contain Thiocarbamide and must be disposed of accordingly. Dispose of in accordance with Federal, State and local regulations. Contact your RD Chemical representative for further information.


ChemPosit Sn (RD-51) is supplied in 100# fiber drums (each containing two pre-measured 50# poly bags). Each bag is suitable for making up a 40 gallon bath.

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