Tin-zinc electrodeposit offers outstanding corrosion protection for steel by combining the barrier
protection of tin with the galvanic protection of zinc, without the bulky corrosion product associated
with wholly zinc deposit. It has high corrosion resistance, especially against sulfur dioxide and salt
water for aircraft parts, automobile components, and equipment used for offshore oilfield applications.
Tin-zinc coating was developed as a direct replacement for environmentally unfriendly cadmium
coating. In this publication, the technical improvements achieved in the electrodeposition of tin-zinc
alloy coating from a newly developed alkaline non-cyanide bath and the structure-corrosion property of
the deposit will be discussed. The 25 ± 5% zinc (balance tin) alloy coating offers excellent corrosion
protection with no obvious white corrosion product. Corrosion test revealed that the deposit offers
protection which is better than cadmium, zinc and zinc-nickel alloy coatings for equal thicknesses. The
tin-zinc deposit obtained from the stannate/zincate bath is fine grained, semi-bright, and shows
considerable improvements over the tin-zinc deposit from the previously used cyanide plating process.
Electron microscopy and X-ray methods reveal microstructural information and structure-corrosion
properties of tin-zinc alloy coating and in the context of its potentials for industrial applications.
KEY WORDS: Tin-zinc alloy coating, electroplating bath, corrosion, microstructure, electrodeposition,
non-cyanide bath.