Susceptibility of welded X80 pipeline steel to corrosion in simulated soil solution

Abstract

This work is focused on the corrosion behaviour of weldments in X80 pipeline steel. In order to clarify their susceptibility to soil corrosion, general corrosion and stress corrosion crack experiments were carried out in a simulated soil solution. Based on these results, the heat affected zone (HAZ) demonstrated higher corrosion susceptibility than the base metal and the weld metal. This was due to both the higher intrinsic corrosion rate of the HAZ and the galvanic effects between the HAZ and the other regions of the weldment. Additionally, in slow strain rate testing, corrosion damage in the HAZ resulted in a significant decrease in fracture area reduction and time to failure and an increase in the appearance of brittle failure on the fracture surface compared with the base metal. Elemental segregation and coarse grains appear to be two factors that lead to the high corrosion of HAZ.

Keywords:

• Pipeline
• Weldment
• Soil corrosion
• Stress corrosion crack

This work was financially supported by the Southwest Petroleum University Foundation (grant no. 2010XJZ178). The help of Dr S. Tang is acknowledged.