Influence of drying temperature on states and physical properties of a dry-in-place type chromate coating which contains Cr (III), Cr (VI), and PO₄^3- were investigated by thermal analysis method. And also the relationship between thermal states and corrosion resistance was studied.
The result of the differential thermal analysis method with the chromate coating at wide range of temperature shows characteristics reactions of inorganic materials.
Endothermic reaction at a range from 85°C till 200°C and exothermic reaction from 200°C till 300°C were found. The chromate coating can be divided into three states from the result of this thermal behavior.
The result of corrosion test of this chromate coated galvanized steel between visual and electrochemical method exhibits the best performance with drying at the end temperature of the endothermic reaction.
It was also proved by values of chromium fixed ratio in coating that chromate coating had several thermal states and exhibited different physical properties as adhesion strength etc.