Susceptibility to external stress corrosion cracking (ESCC) of API X52 pipeline steel in calcareous soil containing different moisture content has been investigated using slow strain rate tests (SSRT). This type of soil is common of the state of Campeche Mexico and has a pH around 8. The results indicate that X52 pipeline steel was susceptible to external SCC only in the saturated calcareous soil, showing some micro cracks in the gage section of the SSR specimen. It was observed that some micro cracks were found at the bottom of micro-pits. Which indicate that first develop a pit and this evolved with time and micro-strain like a crack. Few micro cracks were observed as initiation of SCC close to surface failure. The mechanism of SCC may be influenced by formation and rupture film of carbonates.

This work analyzed the physicochemical effect of the soils typical of the Campeche State of Mexico on the X52 pipeline steel. The susceptibility to external stress corrosion cracking (SCC) of the X52 pipeline steel in two types of soil containing different moisture contents was investigated using slow-strain-rate tests (SSRT). One soil is of a calcareous origin (high pH) and the other is farming soil (near-neutral pH). Generally, steel shows high resistance to SCC in the farming soil, exhibiting only pitting corrosion; however, the X52 steel was susceptible to SCC, though only in the saturated calcareous soil, showing some microcracks in the gage section of SSR specimens. Some microcracks were found at the bottom of micropits. SCC was promoted by the plastic deformation at the bottom of the pits, combined with the influence of the soil chemistry. The process of crack initiation is discussed in terms of the pit geometry and stresses.