RUST-PREVENTIVE STEEL SHEET FOR FUEL TANK AND PROCESS FOR PRODUCING THE SHEET

• Main Authors: OKADA, NOBUYOSHI, OMORI, TAKAYUKI, FUDA, MASAHIRO, SAWADA, KEN, OYAGI, YASHICHI
• Format: Patent
• Language: English; French; German
• Published: 19.03.1997
• Edition: 6
• Subjects: CHEMICAL SURFACE TREATMENT; CHEMISTRY; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING MATERIAL WITH METALLIC MATERIAL; COATING METALLIC MATERIAL; DIFFUSION TREATMENT OF METALLIC MATERIAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; METALLURGY; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION

A rust-preventive steel sheet for fuel tanks having on the surface thereof an alloy layer containing at least one of Ni, Fe, Zn and Sn and having a layer thickness of at most 2 mu m per each side and, formed thereon, a tin-zinc alloy plating layer comprising 40-99 wt.% Sn and 60-1 wt.% Zn, containing at most 20/0.25 mm of zinc crystals with a major diameter of 250 mu m or above, and having a layer thickness of 2-50 mu m per each side, the steel sheet as the base metal containing, on the weight basis, at most 0.1 % C, at most 0.1 % Si, 0.05-1.2 % Mn, at most 0.04 % P, at most 0.1 % Al, optionally at least one of B, Ti, Nb and Cr, and the balance consisting of Fe and inevitable impurities, and a process for producing the sheet which comprises precoating an annealed steel sheet with Ni and Ni-Fe alloy in a Ni content of 0.1-3.0 g/m , coating the sheet with a flux containing 2-45 wt. % (in terms of chlorine) of hydrochloric acid, and plating the sheet by dipping the same in an alloy bath composed of 40-99 wt. % Sn and 60-1 wt. % Zn at a bath temperature ranging from the melting point of the alloy plus 20 DEG C to the melting point plus 300 DEG C for a period of less than 15 sec.