REPUBLIC OF SERBIA

MINISTRY OF DEFENCE

www.mod.gov.rs

MINISTRY OF DEFENCE

Material Resources Sector

Defensive Technologies Department

Military Technical Institute

www.vti.mod.gov.rs

Corrosion testing of AN Al-Zn-Mg-Cu alloy after different heat treatment regimes by THE application of electrochemical methods

BORE JEGDIĆ

Institute GOŠA, Belgrade, bore.jegdic@institutgosa.rs

ANA ALIL

Institute GOŠA, Belgrade, ana.alil@institutgosa.rs

BILJANA BOBIĆ

Institute GOŠA, Belgrade, biljana.bobic@institutgosa.rs

MIROSLAV RADOSAVLJEVIĆ

Institute GOŠA, Belgrade, miroslav.radovanovic@institutgosa.rs

VESNA MIŠKOVIĆ-STANKOVIĆ

Faculty of Technology and Metallurgy, University of Belgrade, vesna@tmf.bg.ac.rs

Abstract: The corrosion tendency in the 7000 series aluminium alloys changes depending on the content of alloying elements, thermal and thermo-mechanical treatments, etc. An alloy of this type applied in the production of weapons and military equipment has been investigated by applying different electrochemical methods. A degree of the precipitation hardening (aging) of the alloy has been evaluated by measuring its electrical resistivity. The corrosion potential measurements (E_corr.) gave information about the distribution of the alloying elements between the solid solution and the precipitation phases. The polarization measurements, performed in the 0.5 M NaCl solution, have shown a more positive value of the pitting potential (E_pit.) and a greater 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 (a higher value of polarization resistance, R_p, and a lower value of capacitance, C_dl) comparing to the one-step aged alloy. These results enable a deeper insight into the effects of both heat treatment and alloying elements, primarily copper, on the corrosion resistance of the tested alloy.

Key words: aluminium alloys, precipitation hardening, corrosion, electrochemical methods, EIS