Loading patent…
AssigneeSumitomo Metal Industries, Ltd.
InventorsHiroyuki Nagai, Yoshihiro Kawanishi, Eiji Kajiyama, Hiroyuki Kashiwagi, Shinichi Tsuchiya
Estimating the term…
A material which can be improved in its resistance to corrosion caused by alcohol-containing fuels after formation without detriment to weldability and without any substantial cost increase is developed. Constitution A chromate film is applied to a Zn--X alloy electroplating layer, in which X is one or more of Ni: 3-18 wt %, Co: 0.02-3 wt %, Mn: 25-45 wt %, or Cr: 8-20 wt %. The Zn--Ni alloy plating layer underlying the chromate film has cracks with a density of 1000-150000 in terms of the number of plated regions surrounded by cracks in a 1 mm.times.1 mm visual field, with cracks having a maximum width of 0.5 .mu.m or less comprising 90% or more of the total number of the cracks, and with cracks having a depth of 80% or more of the thickness of the plating layer comprising 80% or more of the total number of the cracks.
A surface-treated steel sheet exhibiting improved corrosion resistance after forming, which comprises a Zn--X alloy electroplated layer in an amount of 5-50 g/m.sup.2 on at least one side of the steel sheet, an alloy composition of the layer being such that X is at least one substance selected from the group consisting of Ni:
A surface-treated steel sheet exhibiting improved corrosion resistance after forming, which comprises a Zn--X alloy electroplated layer in an amount of 7 g/m.sup.2 or less on at least one side of the steel sheet, an alloy composition of the layer being such that X is at least one substance selected from the group consisting of Ni:
Dependencies are inferred from the claim text.