Toyo Kohan Co., Ltd.

Migita Patent Office

Hitoshi Kuroda

Tsuneo Inui

Kenji Hizuka

Yoshikazu Kondo

Fumio Kunishige

Hideaki Hamano

Katsuhito Yazaki

Tetsuro Hanabusa

Tin-free steel having a first layer of metallic chromium on a steel base and a second layer of hydrated chromium oxide on the first layer, in which the atomic ratio of sulfur and the atomic ratio of fluorine to the sum of chromium, oxygen, sulfur and fluorine in the second layer are respectively not greater than 2.5 atomic percent and not greater than 10 atomic percent. This tin-free steel can be used for a nylon-adhered can body to be subjected to a hot-packing or retort treatment, since it has excellent lacquer adhesion after aging in hot water and under retort conditions.

Tin-free steel can body

Process for producing tin-free steel

An acidic tinplating electrolyte containing at least one sulfate selected from the sulfates of alkaline metals, ammonium, aluminum, manganese or chromium and an ethoxylated .alpha.-naphthol sulfonic acid in a known stannous sulfate or stannous phenolsulfonate electrolyte. This acidic tinplating electrolyte is suitable as a preplating electrolyte for a tinplate in which excellent corrosion resistance is required and also as an electrolyte for the production of a steel sheet having an extremely thin tin layer or an extremely thin iron-tin alloy layer, as a very dense and uniform tin layer is formed on the steel sheet by using the electrolyte of this invention.

Acidic tinplating process and process for producing an iron-tin alloy on

A method for the pretreatment of tin-free steel which comprises a cathodic treatment after an anodic treatment of a degreased steel sheet in an acid chromate electrolyte, said steel sheet consisting of an upper layer of hydrated chromium oxide and a lower layer of metallic chromium. This pretreated tin-free steel has excellent lacquer adhesion after aging in hot water and under retort conditions.

Method for pretreatment in the production of tin-free steel

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Kudamatsu, Japan

Hitoshi Kuroda