Abstract This invention relates to the surface treatment of steel plates or sheets and discloses a novel steel sheet structure, wherein the steel sheet is first electrolytically surface coated with a metallic chromium layer of a thickness not exceeding about 0.1 micron and is then electrolytically plated with a chromate film of a thickness not exceeding 0.1 mg/dm2. The chromium layer thickness should preferably not be less than 0.0016 micron. The inventive steel sheet constitutes a superior can stock and may be provided with a top coat of organic composition. The invention also discloses a two-step process for producing the sheet. Pursuant to this process the metallic chromium layer is first electrolytically deposited on the steel sheet surface, whereupon the chromate film is electrolytically deposited on the metallic chromium layer. An important feature of the invention is that the chromate treatment is carried out in a solution which is devoid of a sulphuric acid radical having a tendency to deposit metallic chromium. Particular process conditions in respect to bath composition, current density and treatment time are disclosed.
Inventors
👤 Hiromu Uchida
👤 Osamu Yanabu
Bibliographic Details
Application Number—
JurisdictionUS
Data Sourcegoogle_patents
Last Synchronized2026-11-01 05:10
CPC Classifications
C; C25; C25D; C25D11/00; C25D11/38
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
150 words
A process of forming a chromate film on a chromium plated steel sheet for use in can making, the chromium layer on the steel sheet having a thickness not exceeding about 0.1 micron, which comprises placing the chromium plated steel plate as a cathode into an electroplating bath consisting essentially of about 50 g/liter of chromic acid and about 2 g/liter of sodium silico-fluoride as a reducing agent and containing no sulfuric acid radicals and continuing the electrolysis until a chromate film having a thickness not exceeding 0.1 mg/dm 2 has been formed on the chromium layer, said electrolysis being carried out at a bath temperature of about 40° C., a current density of 5 amperes per dm 2 and for a treating time of about 2 seconds, said thus coated steel sheet possessing excellent corrosion resistance, adhesion for organic coatings and said film being resistant to deterioration on bending.
Claim 2
Dependent Claim
150 words
A process of forming a chromate film on a chromium plated steel sheet for use in can making, the chromium layer on the steel sheet having a thickness not exceeding about 0.1 micron, which comprises placing the chromium plated steel plate as a cathode into an electroplating bath consisting essentially of about 50 g/liter of chromic acid and about 2 g/liter of sodium silico-fluoride as a reducing agent and containing no sulfuric acid radicals and continuing the electrolysis until a chromate film having a thickness not exceeding 0.1 mg/dm 2 has been formed on the chromium layer, said electrolysis being carried out at a bath temperature of about 40° C., a current density of 5 amperes per dm 2 and for a treating time of about 2 seconds, said thus coated steel sheet possessing excellent corrosion resistance, adhesion for organic coatings and said film being resistant to deterioration on bending.