Effect Of Phytate On The Protection Performance Of Epoxy Coating With Rust

Coating which been applied on the rusty surface is one of the well applied coatings in the nowdays.In some reports,the phosphoric acid or phosphate has been well used in this field because of the reaction of PO₃^3-with Fe³⁺.However,phosphate is the strong acid and has some shortcomings during the utilization such as easily excessive addition,poor overcoat ability,environmental pollution,and so on.Phytic acid which has several phosphate groups,quite strong metal chelating ability and environment friendly has been applied in metal surface treatment.Phytate which has six phosphate groups and quite strong metal chelating ability has been applied in metal surface treatment.However,the experimental study found that the high addition of phytic acid could affect the performance of coating,so this study used phytate as a filler to prepare the coating in epoxy resin.This study mainly discussed whether the phytate could be applied in the coating on rusty carbon steel or not.The results of electrochemistry tests?electrochemical impedance spectroscopy,polarization curve?and surface analysis technologies?scanning electron microscope,energy spectrum,infrared spectrum?indicated:Rusty carbon steel treated with phytate had much smaller corrosion rate in 3.5wt.%NaCl solution than that treated with phosphate acid or tannic acid.This result showed that phytate had good corrosion inhibition for rusty carbon steel.The reaction of phytate with Fe³⁺made the structure of the rust layer more compact.The epoxy coatings with different kinds of phytate were coated on the surface of rusty carbon steel.The results indicated that adding phytate in the epoxy coating could improve the adhesion of the coating,enhance the shielding properties of the coating,and slow down the corrosion rate of the carbon steel beneath the coating.The coating showed the better protection performance when phytic acid potassium was added.2wt.%,5wt.%and 8wt.%phytic acid potassium were dispersed in epoxy coating then were coated on the surface of rusty carbon steel.The results further showed that adding phytic acid potassium could improve the protective performance of epoxy coating for rusty carbon steel.The coating with the addation below 5wt.%phytic acid potassium showed the better protection performance.