Epoxy coatings electrodeposited on steel electrochemically modified by Zn-Co alloys

Abstract

The corrosion behavior of epoxy coatings electrodeposited on steel and steel modified by Zn-Co alloys deposited from chloride and sulphate baths were investigated during exposure to 3 % NaCl. The electrochemical impedance spectroscopy, gravimetric liquid sorption experiments and thermogravimetric analysis were used. It was shown that the almost unchanged values of pore resistance for epoxy coating on Zn-Co alloy deposited from chloride bath were obtained over the entire investigated time, indicating the great stability of this protective system, due to the existence of a pseudo-passive layer of ZnCl2-4Zn(OH)2. Smaller values of diffusion coefficient of water through epoxy coating and smaller amount of absorbed water inside epoxy coating on steel electrochemically modified by this Zn-Co alloy also prove better protective properties in respect to epoxy coating on other investigated substrates.

Ispitivani su koroziono ponašanje i transportne osobine epoksidnih kataforetskih prevlaka na čeliku i čeliku modifikovanom Zn-Co legurama tokom delovanja 3% rastvora NaCl. Iz rezultata dobijenih metodom spektroskopije elektrohemijske impedancije (otpornosti elektrolita u porama kapacitivnost prevlake), gravimetrijske metode određivanja sorpcionih karakteristika (koeficijenta difuzije vode) i termogravimetrijske analize (sadržaj vode u prevlaci) pokazano je da modifikacija površine osnovnog supstrata značajno utiče na elektrohetnijske osobine i korozionu stabilnost epoksidnih prevlaka.