Highly corrosion-resistant zincate type zinc-iron-phosphorus alloy plating bath and plating method using the plating bath

摘要

A zinc-iron-phosphorus alloy-plating bath having a pH of not less than 13 and containing iron, phosphorus and zinc sources in amounts required for electro-depositing a zinc-iron-phosphorus alloy film having an iron content ranging from 0.1 to 30% by weight, a phosphorus content ranging from 0.001 to 1.5% by weight and the balance of zinc, and an auxiliary agent for depositing phosphorus. The use of the alkaline plating bath permits the formation of a zinc-iron-phosphorus alloy film, through plating, excellent in lustre of deposit, throwing power and corrosion resistance and the reduction in corrosion of the plating equipment and also permits the formation of a film, through plating, having excellent adhesion as an undercoat for painting.