Detection of Zinc Diffusion into Tin Coatings on Brass

SYNOPSIS

The corroding potentials, in 0·01 % NaC1 solution, of tin containing small amounts of zinc are initially zinc-like and become tin-like only after immersion in the solution for a time which depends on the zinc content. Potential measurement can be used to detect the diffusion of zinc into tin coatings on brass during flow-brightening or long storage. The small amounts of zinc detected by this means are sufficient to cause, in exposure to copious condensation of moisture, the formation of corrosion products which make soldering more difficult, although they do not affect the soldering of the coating if it is stored normally.