Inland Steel Company

Harvie Ho Lee

Yong-Wu Kim

David W Gomersall

Harry P Leckie

The loss of zinc by vaporization when heating a zinc-aluminum coating to a temperature between about 427.degree. C. and 816.degree. C. (800.degree. F. and 1500.degree. F.) is significantly reduced by applying a zinc-aluminum coating containing about 30 to 75 weight percent zinc and the balance essentially aluminum to a mild carbon steel base which contains titanium in an amount sufficient to combine with all of the carbon in the steel and provide a small excess of uncombined titanium in the steel base, thereby providing a zinc-aluminum coated steel article which has improved corrosion and oxidation resistance when heated at temperatures between about 427.degree. C. and 816.degree. C. (800.degree. F. and 1500.degree. F.).

Reduction of loss of zinc by vaporization when heating zinc-aluminum

A ferrous metal strip is continuously hot-dip coated with a zinc-aluminum alloy by immersing the metal strip in a hot-dip coating bath containing between about 0.2 wt. percent and 17 wt. percent aluminum, between about 0.02 wt. percent and 0.15 wt. percent lead, and between about 0.03 wt. percent and about 0.15 wt. percent magnesium with the balance essentially zinc. In a further embodiment the hot-dip alloy coating can also contain between about 0.1 wt. % and 0.3 wt. % copper. The resulting hot-dip zinc-aluminum alloy coatings when applied to a ferrous metal strip exhibit good resistance to intergranular corrosion and blistering when exposed to a high humidity atmosphere and form smooth surface coatings which have good formability both in the 'as coated' state and after prolonged storage in a high humidity atmosphere.

Method of hot-dip coating a ferrous substrate with a zinc-aluminum alloy

A ferrous metal strip is continuously hot-dip coated by immersing the metal strip in a hot-dip coating bath containing between about 0.2 wt. percent and about 17 wt. percent aluminum, between about 0.02 wt. percent and about 0.15 wt. percent antimony while excluding lead in amounts more than 0.02 wt. percent, and the balance being essentially zinc. Smooth bright coatings are formed which are highly resistant to intergranular corrosion and blistering when exposed for an extended period to a hot humid atmosphere, have good formability in both the as coated state and after prolonged exposure to a hot humid atmosphere, have a markedly reduced susceptibility to the formation of white rust, and have a reduced rate of general surface corrosion without any diminution of the mechanical properties of the coating.

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Glenwood, IL, United States of America

Harvie Ho Lee