The Unified Mechanism of Corrosion in Aqueous Weak Acids Solutions: A Review of the Recent Developments in Mechanistic Understandings of Mild Steel Corrosion in the Presence of Carboxylic Acids, Carbon Dioxide, and Hydrogen Sulfide

The recent developments in mechanistic understandings of mild steel corrosion in the presence of carboxylic acids, carbon dioxide, and hydrogen sulfide, when place side by side, reveal a simple, universal mechanism despite all the differences conventionally presumed for these corroding systems. These findings are recast into a generic mechanistic view of corrosion in aqueous weak acid solutions herein. In this mechanism, the buffering effect resulting from the chemical dissociation reaction inside the boundary layer, is highlighted as an inherent property of all weak acids. The validity of this mechanism was further examined through mathematical experimentation based on a comprehensive mechanistic model. It is shown that this mechanism is able to account for a wide range of characteristic behavior of cathodic currents, including those previously associated with the direct reduction reactions. The results are ultimately presented as a simple and generic categorization of weak acids based on their pK(a) values to serve as a basis to assess the detrimental effect of any weak acid on mild steel corrosion in aqueous acidic solutions.