The Effect of Jet Flow Impingement on the Corrosion Products Formed on a Pipeline Steel in Naturally Aerated Sour Brine

Abstract

Corrosion was generated by the action of a jet impingement flow of sour brine on pipeline steel samples of X70. Flow assisted corrosion affected nature, number and peak intensity of the chemical species formed as corrosion products. Iron sulfides predominated in static and low flow rate conditions (1.1 m/s), whereas at 2.4 m/s iron oxides were mainly formed, which led to higher corrosion rates and suggested that oxides are less protective than sulfides. On inhibition, imidazoline seems to mitigate oxide formation and support sulfide formation balancing both species on steel surface. Ferrite phase in laminar pearlite was preferentially dissolved with/without inhibitor and mackinawite (FeS 2 ) was formed at every flow rate, angle with and without inhibitor. Theoretical stresses determined by computational flow dynamics for corrosion product removal showed a fair approximation to those proposed in the literature.

Surface analyses of corrosion products formed on API X-70 steel in sour brine after testing in a pipe loop

“…Other sulfides and/or sulfates might precipitate depending on pH, temperature, flow rate and oxygen content. It is thought that marcasite (FeS 2 ) might led to the presence of minor content of mikasaite, Fe 2 (SO 4 ) 3 , in corrosion products, after H 2 SO 4 is formed when H 2 S is dissolved in water so general corrosion and localized corrosion might appear; the former because of the continuous formation of FeS and the other due to film porosity that under certain conditions might lead to hydrogen embrittlement [36].…”