| 摘要 |
PURPOSE:To provide a titled phosphate treating liquid with which an electrogalvanized steel sheet having excellent whiteness is obtainable by consisting essentially said liquid of zinc phosphate and further adding a specific concn. of hydrogen peroxide thereto. CONSTITUTION:A steel sheet 7 getting out from a galvanizing vessel 1 is subjected to a pretreatment of alkali cleaning in a surface conditioning vessel 2 and is then subjected to a spraying or dispping treatment by a phosphate treating liquid in a phosphating vessel 3. After the steel sheet is washed in a washing tank 4, the steel sheet is subjected to a sealing treatment with a dilute chromic acid in a sealing vessel 5 and is dried with a dryer 6 by which the electrogalvanized steel sheet is obtd. The above-mentioned phosphate treating liquid is formed by consisting the same essentially of zinc phosphate, adding a very small amt. of nickel and fluorine ion thereto and further adding hydrogen peroxide at a concn. of 1-5g/l thereto for the purpose of accelerating film formation. The treated steel sheet having about >=60 whiteness is thus stably obtd. |
