FACTORS INFLUENCING THE RESISTANCE OF STEELS TO WET HYDROGEN SULPHIDE STRESS CORROSION
The aim of this research was to determine the influence of some alloying elements and of their microstructure on the corrosion behaviour of grade X60 to X70 pipe line steels (produced by controlled rolling followed by accelerated cooling), under the influence of wet H(2)S. As regards the microstructure of the steel and its effect, acicular ferrite appeared to be beneficial in avoiding sulphide stress corrosion cracking. Concerning the chemical composition of the steel, the detrimental roles of sulphur and phosphorus were identified, the latter element causing cracking, due to its very high concentrations. Carbon was to be limited in order to i) favour the formation of an acicular ferrite type microstructure and ii) reduce the influence of manganese. Molybdenum appears to have a detrimental effect, owing to its tendency to promote bainite formation during accelerated cooling. Neither copper nor nickel had any influence under the NACE test conditions. Under the BP test conditions however, where a higher pH value was used, copper was very beneficial. The influence of microprecipitates was investigated and was seen to depend on the size and distribution of these particles in the steel matrix. Finally, the presence of a welded zone was found to have a detrimental effect on the corrosion behaviour of steels, even when the base steel passed the test.
Bibliographic Reference: EUR 12200 EN (1989) 81 PP., MF, ECU 4, BLOW-UP COPY ECU 11.25 THE OFFICE FOR OFFICIAL PUBLICATIONS OF THE EUROPEAN COMMUNITIES, L-2985 LUXEMBOURG
Record Number: 1989128035000 / Last updated on: 1992-08-10
Original language: EN