Study Of Calcium Ions Effect On Pitting Corrosion Using Electrochemical Noise Analysis (Ecn)

In oil and gas exploration and production, carbon steel represents the most commonly used construction material for pipelines. Carbon steel pipelines experience corrosion in the form of uniform or localized attack. Due to the presence of cations such as Ca2+ in the formation water, the cations could precipitate as scale deposit and may influence the susceptibility to pitting corrosion. The objective of the study is to investigate the susceptibility of X52 mild steel to pitting corrosion and the corrosion behavior in NaCl solution with varies concentration of calcium ion by using electrochemical noise analysis. In this project, the three conditions which are: 3% NaCl solution, 3% NaCl + 1.5% CaCl2 solution and 4.6% NaCl solution (equivalent Cl- concentration to 3% NaCl + 1.5% CaCl2 solution) saturated by CO2 at 45°C were used. The results showed that under stagnant condition the initiation period of pitting corrosion decreased with increasing Cl- concentration, but at the same Cl- concentration, Ca2+ could prolong the initiation period. The result showed that the corrosion rate increase with the increase of chloride ion concentration but decrease with existence of calcium ion. The result of the experiment has shown that the data by using electrochemical noise analysis are effective in measuring corrosion rate as well as pitting initiation time.