Effect of sulfur compounds on formation of protective scales in naphthenic acid corrosion in non-turbulent flow

• Published in: Corrosion science 2018-02, Vol.131, p.223-234
• Main Authors: Jin, Peng, Robbins, Winston, Bota, Gheorghe
• Format: Article
• Language: English
• Subjects: A. Carbon steel; Acids; B. SEM; B. TEM; C. Acid corrosion; C. High temperature corrosion; Carbon steel; Computational fluid dynamics; Corrosion; Corrosion products; Corrosion tests; Naphthenic acids; Oxygen; Scale (corrosion); Scale (ratio); Scale formation; Studies; Sulfur; Sulfur compounds; Turbulence; Turbulent flow
• ISSN: 0010-938X; 1879-0496
• DOI: 10.1016/j.corsci.2017.11.027

[Display omitted] •Under replenishing conditions, oxide layers were not formed in corrosion by model acids only.•Oxide layers were formed in concurrent corrosion by model acids and sulfur compounds.•Scale protectiveness can be explained by diffusion of ferrous ions through magnetite and iron sulfide. Naphthenic acids corrosion is generally considered to leave no corrosion product on steel surface. However, our prior research demonstrates that a protective oxide scale is formed in corrosion with model acids under stagnant conditions. In present study, the corrosion by model acids and a reactive sulfur compound has been investigated alone and in combination in a flow through system. None of the model acids alone forms an oxide scale. However, mixtures of the acid and sulfur compound form a protective scale consisting of an oxygen-containing layer underneath a sulfide layer. A mechanistic model of corrosion and scale formation is proposed.