Zinc Phosphating Accelerated by Rare Earth Nitrate on Aluminum Alloy

The influence of rare earth nitrate(REN) on the zinc phosphate coatings on aluminum alloy was studied by means of scanning electron microscopy(SEM),X-ray diffraction(XRD),energy-dispersive X-ray(EDX) and electrochemical measurements.The results showed that REN possessed good capacity to transport oxygen and debase polarization of cathode,and markedly accelerated phosphate deposition and consumedly decreased zinc phosphate crystal size.The chemical composition of zinc phosphate coatings varied as the REN concentrations of the phosphating solutions changed,but REN was not incorporated into zinc phosphate coatings.The phosphate coatings formed in phosphating solutions with REN had lower chemical reactivity than those formed without REN,and the corrosion resistance had been improved.