Role of red mud in natural passivation and chloride-induced depassivation of reinforcing steels in alkaline concrete pore solutions

The influence of red mud (RM) on electrochemical behaviour, chemical composition, surface morphology and thickness of passive films naturally formed on low-carbon steel and 2304 stainless steel in alkaline concrete pore solutions was investigated using electrochemical measurements, XPS, AFM and SEM/EDS. Furthermore, chloride-induced pitting corrosion of passivated steels was characterized with and without RM. Results show that RM was detrimental to the passivity of steels by forming defective passive films with reduced thickness. Despite the formation of a less protective passive film on low-carbon steel, beneficial role of RM was highlighted in preventing chloride-induced depassivation and corrosion propagation.

Automated summary

Red mud (RM) has a detrimental effect on the passivation of steels, leading to the formation of defective and thinner passive films. Despite this, RM plays a beneficial role in preventing chloride-induced depassivation and corrosion propagation.