Chromium-Free Organic Treating Solution For Galvanized Steel Sheet

Now organic coatings without 6-valent chromium are promising candidates of anti-fingerprint technology.In this article, carried out Salt spray test, XRF, SEM(Scanning electron microscope), Electrochemical impedance spectroscopy, XPS(X-ray photoelectron spectroscopy) etc as my test method to value the characteristcs of the chromium-free steel sheet with organic coating.In the salt spray test, the treatment solution with ammonium meta-vanadate provided provided an result of no rust through 72 hours. So good corrosion protection can be obtained in such a thin film without the use of chromate.when the mass of reducing agent is 50% by mass of ammonium meta-vanadate,sheet can gain no rust in salt spray test after treating;the parts of ammonium meta-vanadate preferably is 2%;pH and the phosphoric acid influent properties of coating;to obtain more time aginst corrosion, pH=2and the concentration of phosphoric acid is chosen for 2%.Trough XPF,EIS,XPS methods, the thickness of coating can be easily controlled in the range of 0.4μm ~1μm; EIS can be used for the evaluation for the course of corrosion;Znic in the surface of coating exist as ZnO and Zn(OH)2, this result proved that passivation has occurred by the use of ammonium meta-vanadate;moreover, instability of treating agent can probably be caused by the resin, used in treating solution , in some situation.