The Effect of Preferential Weld Corrosion Study in CO2 Capture Plant at PFK

This paper discusses on the leakages issue due to severe localized corrosion attack along the pipeline (made from ASTM 106 B carbon steel) in the CO2 capture plant of PETRONAS Fertilizer Kedah (PFK) which its cause is still uncertain. The suspected cause was corrosion occurred to the high residual stresses trapped in the weldment region of the pipelines as the pipelines did not undergo post-welding heat treatment to release the stresses. The pattern of the corrosion suggested that Preferential Weld Corrosion (PWC) could have taken place in the pipelines. In order to investigate the relation of PWC and the leakages issue in PFK, the contribution of self corrosion rate of the Parent Metal, HAZ and Weld regions under the various conditions that includes saturated CO2, different concentration of caustic, KS-1, and under the temperature of 50oC will be studied. The methodology selected consists of EIS and LPR tests plus a basic metallographic observation between the three regions; Parent Metal, HAZ and Weld. It was found that when the corrosion rate is the highest under the condition of saturated CO2, 500ppm caustic, 250ppm KS-1 with 50oC and the Weld region has the highest corrosion rate in comparison with Parent Metal and HAZ regions for all conditions. It is therefore, concluded that the Weldment region (consists of HAZ and Weld) is prone to corrosion attack in comparison to Parent Metal region that was unaffected by the welding process. In the pursuit of a better answer to the issue, it is recommended that a research is done on the behavior of the different regions of the affected pipeline and to study further on the possible corrosive mixture of CO2, caustic and KS-1. Meanwhile, stress relieve heat treatment is suggested to be conducted on the welded pipelines to mitigate the corrosion problem.