The phosphate layer is generally applied by spray or dipping into a phosphating solution. A phosphate coating is a transition layer in several respects. It is less dense than most metals but more dense than coatings. It has thermal expansion properties which are intermediate between that of the metal and the coating. The result is that phosphate layers can smooth out the sudden changes in thermal expansion which would otherwise exist between the metal and the paint.
Phosphate coatings are porous and can absorb the coating.
Upon curing, the paint solidifies, locking into the phosphate pores. Adhesion is greatly enhanced. Combined cleaning and phosphating. 1.0 to 1.5 minutes at 100 degrees F to 150 degrees F. 2. Chromic acid rinse or deionized water rinse.