Influence of NaCl concentration on pitting corrosion of extruded Al-Mg-Si alloy AA6060

Abstract

Extruded Al-Mg-Si alloys (AA6xxx series alloys) are the most common aluminum alloys for structural application due to reliable mechanical characteristics and corrosion properties. Spontaneously formed adherent aluminum oxide film on the surface protects Al and Al -alloys from corrosive attack in neutral media, but in chloride containing solutions, such thin and compact passive film is prone to breakdown. In this study the corrosion behavior of commercial extruded Al-Mg-Si alloy AA6060 was investigated in NaCl solutions of different concentrations using anodic potentiodynamic polarization measurements under deaerated conditions at room temperature. It was shown that sensitivity to chloride attack increase with increasing Cl- concentration and depends on cathodic micro constituents in extruded Al-Mg-Si alloy.Ekstrudirane Al-Mg-Si legure (serija AA6xxx) najčešće se koriste u konstrukcijske svrhe zahvaljujući prihvatljivim mehaničkim i korozijskim svojstvima. Spontano formirani sloj aluminijeva oksida na površini Al i Al-legura štiti od korozijskih oštećenja u neutralnim medijima, ali u otopinama koje sadrže kloride dolazi do proboja takvog tankog i kompaktnog pasivnog filma. Kao posljedica tog procesa, nastaju na površini lokalna oštećenja i dolazi do pojave jamičaste korozije- pitinga. U ovom je radu proučavano korozijsko ponašanje komercijalne ekstrudirane Al-Mg-Si legure AA6060 u otopinama NaCl različite koncentracije, metodom anodne potenciodinamičke polarizacije u deaeriranim uvjetima pri sobnoj temperaturi. Pokazalo se da sklonost lokalnoj koroziji raste s koncentracijom kloridnih iona i ovisi o katodnim mikrokonstituentima u ekstrudiranoj Al-Mg-Si leguri.