Corrosion Preventive Effect of Ultraphosphate Film on Iron and Steel Surfaces

Abstract

The rust preventive effect of the phosphate coating process has its origin in the strong bonding that exists between the OH groups of phosphoric acid and the iron atoms, and in the poor electric conductivity of the phosphate film. This study was undertaken in the hope that rust preventive effect could be improved by the use of linear polyphosphate or reticular ultraphosphate.
It was found that the ultraphosphate film had a rust preventive effect superior to that of the orthophosphate film, especially when the film was formed on a rusty steel surface. A theoretical explanation of the results is presented.