Equipment for Immersion Systems

An immersion phosphating system for all types of coatings (zinc, manganese, and iron) should include:

• Required number of tanks

• Temperature and solution-level controls

• Overflow and drainage systems

• Vapor-exhaust systems

• Material-handling devices

When drums are used to contain the parts, devices are required at each tank to rotate the drums at approximately 4 rev/min while the drums and the parts within are submerged.

Phosphating tanks are usually made from low-carbon steel plate about 6 mm (-4 in.) thick. A tank and drum for immersion phosphating small parts are shown in Fig. 4. The normal life of a low-carbon steel tank for zinc phosphating solution under average operating conditions is about 1 year. However, some companies report 2 to 3 years of service. One

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