A Study on Low Temperature Phosphating for Cold Forming

Zinc phosphating for cold forming of steel was studied with emphasis on decreasing phosphating temperature. To lower phosphating temperature, some techniques, such as adding Cu ion into bath, using activator in the form of pre-dip, and aeration in bath, instead of using conventional accelerator, namely oxidizing agent, have been tried. It was revealed that phosphating, leading to coatings of Improved uniformity and fine crystal size, can be carried out using above techniques at lower temperature ($55^{\circ}C$) compared to conventional phosphating temperature ($80 ~ 90^{\circ}C$ ). Under present condition, it was seen that optimum concentrations of Cu ion in phosphating bath and activator in pre-dip are 0.015% (w/w) and 2.0 g/1, respectively. The coating weight was within the range of 15 ~ 20 g/$\m^2$. When lubricant was applied into phosphating coatings, the amount of lubricating component (total soap) was found to be 6 ~ 10 g/$\m^2$ and the lubricated panel revealed excellent lubricating properties.

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