| 摘要 |
PURPOSE:To obtain a zinc type surface treated steel material of superior corrosion resistance in an atmospheric corrosive environment accelerated by chlorine ions by applying phosphating further to the surface of various plated steel materials contg. zinc. CONSTITUTION:A steel material having the surface layers wherein the lower layer is coating layer of 2-200g/m<2> built-up quantities consisting of 20-95% Zn, and the balance >=1 kind of metals other than Zn, their compounds and Zn compounds, and the upper layer is a coating layer of 0.05-8g/m<2> built-up quantities contg. >=60% phosphate. If the Zn in the lower layer is below 20%, protective effect is insufficient, and above 95%, the protective film is unstable. If the built-up quantities of the lower layer are below the lower limit, the surface cannot be fully coated, and above the upper limit, workability is poor and the film is liable to peel. Next, the phosphate stabilizes zinc hydroxide films but if it is below 60%, the effect is insufficient. If the built-up quantities of the upper layer are below the lower limit, the surface cannot be fully coated and the upper limit is the limit of ordinary industrial methods. |
