Method for replenishing chemical in zinc phosphate treatment

摘要

A method for replenishing a nitrite accelerated zinc phosphate treating liquid for forming zinc phosphate coatings on metal surfaces, wherein the metal surface is treated at the rate of 3 to 15 m2 per hour per cubic meter of treating liquid and the treating liquid is replenished with free phosphoric acid at the rate of 0.10 to 0.31 moles per 10 m2 of treated surface area.