STUDY OF PITTING CORROSION BEHAVIOR FOR ALUMINUM ALLOY 1100 IN 3% NaCl SOLUTION

Abstract

Pitting corrosion behavior of aluminum alloy 1100 was studied in this investigation in a neutralized and aerated 3% NaCl solution and all experiments were performed at room temperature. There were four groups of specimens to be studied: 1. As received, 2. Annealed at 760 oC, 3.Cold 35% rolling, and 4. 75% rolling. Numbers of pits was countered, and pits depth was measured by used digital photo fixed on a microscope a digital photos were taken The numbers of pits increase as duration increase within the period of (5-90) days. The graduation of increasing is mostly uniform for all groups' leads to the conclusion that nucleation and initiation of pits are continuing with the continuity of pits growth. Also it was observed that the annealed specimens have the lowest tendency (0%) to corrode by pitting and this tendency increase forwarding as follows: Annealed < as received < rolling 35 %< rolling 75%. Also it was observed that maximum depth of pitting increases gradually with duration for all groups. Also it was proved that metallurgic factor (cold rolling) increase with increase pits number, maximum pit depth and pit growth towards depth. Probability of pits appear was observed to be increased with duration for all groups and it is high expected for the shallow pits, in contrast for the deep pits. Through the examination of pit's normal distribution due to its number and depth, it was concluded that the recent pits depth and due to their high rate of growth will reach the same depth of the recent one leads to a mean value of depth for all. It was concluded that morphology and concentration of pitting are function of duration and specimen treatment. Pitting concentration increases with duration.