Nippon Paint Compnay, Ltd.

Akiko Sueyoshi

Ryoichi Murakami

Shoji Oka

In a method for phosphating the surface of a metallic substrate by treatment with a phosphating solution containing nitrite ions as the accelerator, an improvement wherein the supply of the nitrite ions to the phosphating solution is carried out by electrolytic reduction of nitrate ions present in the phosphating solution while changing the direction of the current flow at a fixed interval of time, whereby a desired concentration of nitrite ions in the phosphating solution is maintained without accumulation of alkali metal and/or ammonium ions unavailable for the phosphating and also without accumulation of precipitates on the electrode, and a uniform phosphate coating film having satisfactorily good coating properties is formed on said surface.

Phosphating of metallic substrate

In a method for phosphating the surface of a metallic substrate by treament with a phosphating solution comprising nitrite ions as the accelerator, an improvement wherein the supply of the nitrite ions to the phosphating solution is carried out by electrolytic reduction of nitrate ions present in the phosphating solution, whereby a desired concentration of nitrite ions in the phosphating solution is maintained without accumulation of alkali metal and/or ammonium ions unavailable for the phosphating and a uniform phosphate coating film having satisfactorily good coating properties is formed on said surface.

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Osaka, Japan

Akiko Sueyoshi