Behavior of Fe-Sn Alloy Formation on Low Tin Plated Surface of Ni Flash-coated Steel Substrate

The behavior of Fe-Sn alloy formation on low tin-plated surface of Ni flash-coated steel substrate was studied at stoving temperature for lacquer coating. The results are as follows:1) Making Ni flash coating amount as 15 mg/m2 on steel substrate and limiting the amount of alloyed Sn to 400 mg/m2 and less through the reflowing process for tin-plated surface eliminate the unfavorable influence of cathodic passivation on the increase of Fe-Sn alloy during stoving and assure the minimum formation of unfavorable Fe-Sn alloy to weldability after lacquer coating.2) The developed low tin plated steel sheet product from an electrolytic tinning line has a "dewy" ap-pearance of melted tin.3) Flash-coated Ni on steel substrate decreases the rate costant for Fe-Sn alloy growth during stoving of the developed product. The Fe-Sn alloy on the developed product after stoving is determined as a phase of very compact FeSn2, but contains the Ni flash coated on the substrate. The crystal orientation of FeSn2 on the product after stoving shows a strong preference for (002) plane.4) The accelerating effect of Cr passivation film on Fe-Sn alloy formation during stoving is derived from CrEC in the passivation film. The increment of CrEC amount in Cr passivation film correlates linearly to the increment of Fe-Sn alloy amount during stoving.