Corrosion properties of an aluminium alloy 7000 series after a new two step precipitation hardening

Abstract

Corrosion properties of an aluminium alloy 7000 series were investigated by different electrochemical methods. The alloy was subjected to the one-step and to a new two-step precipitation hardening. Polarization measurements in the 3.5 wt. % NaCl solution have shown a more positive value of the pitting potential (Epit) and a higher corrosion resistance for the two-step aged alloy. The electrochemical impedance spectroscopy (EIS) has also shown that the two-step aged alloy has better corrosion properties (higher value of polarization resistance, Rp, and lower value of double-layer capacitance, Cdl) comparing to the one-step aged alloy.

Otpornost prema koroziji aluminijumske legure serije 7000 ispitivana je primenom različitih elektrohemijskih metoda. Legura je bila podvrgnuta jednostepenom i novom dvostepenom termičkom taloženju. Polarizaciona merenja u 3,5 mas.% NaCl su pokazala da legura posle dvostepenog termičkog taloženja ima pozitivniju vrednost potencijala pitinga (Epit) i veću otpornost prema koroziji. Spektroskopija elektrohemijske impedancije (SEI) je takođe pokazala da legura posle dvostepenog termičkog taloženja ima bolju otpornost prema koroziji (veću vrednost polarizacione otpornosti, Rp i manju vrednost kapacitivnosti dvojnog sloja, Cdl) u poređenju sa legurom posle jednostepenog termičkog taloženja.