Corrosion of Pipeline Steel in Dry and Wet Alternative Environment

Corrosion behaviors of X80 steel in alternating wet and dry environment were studied by the means of weight loss, electrochemical polarization curves and morphology observation in the NS4 solution. The results showed that the corrosion rate first increased and then decreased with decreasing the time ratio of dry to wet. When the time ratio of dry to wet was 9 h/15 h, the corrosion rate reached 0.56 mm/a which was 1.8 times of the corrosion rate under the condition of full immersion. Under the condition of interval immersion, the corrosion rate decreased with pH value increase. As the concentration of Cl- increased, the corrosion rate first decreased and then increased. The influence sequence on the interval immersion corrosion was time of wet-dry alternating, pH and Cl- concentration on the basis of analysis using gray relational theory.