Letter 13029

Salt Spray Corrosion Comparison 

A customer asked: What is the expected salt spray resistance using cathodic Electrocoat on top of Tricationic low Zinc phosphate? What is the increase, if any of the salt spray resistance if a Powdercoat finish is applied to the above? If anyone has data I would appreciate it.

Thanks,

Steve Wade
Chemetall-Oakite - Romulus, MI

Cathodic Electrocoating can give 1000 hours of salt spray resistance in accordance to test standard ASTM B-117 [link is to spec at TechStreet]. The choice of pre treatment is more of function of the base metal. However, it needs to be compatible with CED system. The second part of the question is tricky! CED coating normally has a DFT of 20 microns or .8 MIL. A final coat of powder coating on it will not improve upon the salt spray test resistance under the test standard ASTM B 117. However, if a test is carried out without the inscribed cross, the thicker the film the better it may perform.

Gurvin Singh Coatec India - Mohali, Punjab, India

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