Investigation of Tin as a Constituent of Inorganic Coatings for Magnesium Alloys.

摘要

A series of tests was initiated to evaluate tin as a filler material in inorganic coatings to be used as a coating for magnesium alloys. Coatings were made based on tin powder incorporated in alkali silicate, quaternary ammonium silicate and chromate/phosphate binders. Tests were run evaluating zinc immersion, stannate, pyrophosphate, and galvanic anodize pretreatments. Salt spray testing indicated alkali silicate coatings with galvanic anodize pretreatment showed improved results. Tin-cadmium and tin-zinc alloys were tested in place of tin powder. Tests were run on ethyl silicate based coatings. Modification of alkali silicate/tin coatings were made with soluble salts to cause controlled leaching; these salts included amine salts, permanganates, and tin compounds. Strontium chromate and EDTA salts were used in primer coatings; these coatings showed some improvement in salt spray resistance. Additions of alkaline leaching materials were made consisting of magnesium oxide and aluminum hydroxide in the alkali silicate/tin coatings. When tested as primer coating with paint systems failure resulted during heat cycle/salt spray testing.