Corrosion Resistance and Film Formation Mechanism of Environmental Protection Steel Passivation

Abstract

The phenomenon of steel corrosion is becoming more and more common.Phosphating is commonly used in industry as a method to prevent steel corrosion，but it causes serious environmental pollution.In order to reduce phosphorus pollution，an environmentally friendly steel passivation process based on phytic acid solution was developed aiming at the base material of Q235 steel，and the corrosion resistance of the environment-friendly steel passivation film was tested by copper sulfate drop test and electrochemical method.Additionally，the composition and microscopic morphology of the passivation film were observed by scanning electron microscope (SEM).Results showed that the average time of copper sulfate drop after passivation reached 107 s，and the corrosion current was only 4.3×10-3mA.Furthermore，the impedance diameter and modulus of the passivated film treated by such environmentally friendly process was large，and its corrosion resistance was higher.Meanwhile，the environment-friendly passivation film was found to be complete without any cracks when it was observed by scanning electron microscope，indicating a good corrosion resistance.Finally，the film-forming mechanism of the environment-friendly passivation film was briefly analyzed.

Keywords

• environmentally friendly passivation|steel|film-forming substances|low phosphorus；corrosion resistance|film-forming mechanism