The effect of Zn-Ni sublayers on the corrosion behaviour and thermal stability of epoxy coatings electrodeposited on steel

Abstract

The electrochemical and transport properties, as well as the thermal stability of epoxy coatings electrodeposited on steel and steel modified by Zn-Ni alloys were investigated during exposure to 3 % NaCl. The Zn-Ni alloys were electrodeposited on steel using direct and pulse current. From the time dependence of the pore resistance of the epoxy coating (impedance measurements), the diffusion coefficient of water through the epoxy coating (gravimetric liquid sorption measurements) and the thermal stability of the epoxy coating (thermogravimetric analysis), it was shown that Zn-Ni sublayers significantly improve the corrosion stability of a protective system based on an epoxy coating. The values of the pore resistance were almost unchanged over a long period of immersion time for epoxy coatings on steel modified by Zn-Ni alloys, inidicating the great stability of these protective systems. .

Proučavane su elektrohemijske i transportne karakteristike i termička stabilnost epoksidnih elektroforetskih prevlaka na čeliku i čeliku modifikovanom Zn-Ni legurama tokom delovanja 3 % rastvora NaCl. Legure Zn-Ni su taložene na čeliku konstantnom i pulsirajućom strujom. Na osnovu vremenske zavisnosti otpornosti u porama epoksidne prevlake (impedansna merenja), koeficijenta difuzije vode kroz epoksidnu prevlaku (gravimetrijsko određivanje sorpcionih karakteristika) i njene termičke stabilnosti (termogravimetrijska analiza), pokazano je da Zn-Ni podslojevi značajno povećavaju korozionu stabilnost zaštitnog sistema na bazi epoksidne prevlake. Skoro nepromenjene vrednosti otpornosti u porama tokom dugog perioda delovanja korozionog agensa kod epoksidnih prevlaka na čeliku modifikovanom Zn-Ni legurama ukazuju na veliku stabilnost ovih zaštitnih sistema. .