Characterisation and comparison of corrosion products originated in steel pipelines transporting sour gas and crude oil

In this work, X-ray diffraction and Mossbauer spectroscopy techniques were used to characterise and carry out a comparison of the corrosion products obtained during the pigging activities in two sour-hydrocarbon-transporting pipelines located in the Gulf of Mexico: the first one being a gas pipeline and the other one a crude oil pipeline. The results indicate that for these specific conditions, there are differences between the corrosion products formed in each pipeline. Iron sulphides and oxides were the main corrosion products and their presence is directly related to the operating conditions prevailing in the pipelines as well as to the hydrocarbon quality. As for the sour gas pipeline, higher concentrations of greigite and pyrite were observed, whereas more proportions of magnetite, mackinawite and marcasite were found in the sour crude oil pipeline. The most important parameters in the formation of the different types of corrosion products are the water content, hydrogen sulphide concentration and ox...