食塩水中でのアルミニウム合金の耐食性と耐孔食性に及ぼすＳＯ４｀２−´とＨＣＯ３｀−´イオンの効果

Abstract

Immersion corrosion tests and electrochemical measurements were carried out to clarify the effect of Cu--SO4--, HCO3-and Cu++ions on the corrosion and pitting corrosion resistance of aluminum and Al-Mg-Zn alloy in NaCl solution. Though SO4--ion has a remarkable corrosion suppressing effect, it promotes pitting corrosion of aluminum in the solution containing Cu++ion. Little apparant pitting corrosion, on the other hand, can be observed on the Al-Mg-Zn alloy in all the solutions examined. These facts can be well understood in terms of anodic and cathodic polarization characteristics in the solutions containing these ions. The probability of pitting corrosion in the solution containing Cu++ion can be estimated in terms of the critical current for pitting initiation in the anodic polarization curve, but not of the pitting potential. The anodic dissolution test at a constant current density will be useful for estimation of pitting corrosion resistance of aluminum alloys.