Laser surface treatment to inhibit observed corrosion of reinforcing steel in sulphate: alkaline media

Abstract

Purpose -The effect of chlorides on corrosion of reinforcing steel is well documented in the literature. However, few studies have focused attention on the effect of sulphates on the corrosion of low carbon steel in alkaline media. This paper aims to address this issue. Design/methodology/approach -This paper describes the results of the investigation into the corrosion behaviour of low carbon steel (typically used as reinforcing steel), exposed to alkaline media at a pH of 9 and 12 with varying concentrations of sulphate and chloride ions, as well as, in sulphate only solutions. An attempt was made to inhibit corrosion of steel exposed to the corrosive media using laser surface treatment of the steel specimens. Mass loss tests and electrochemical tests were conducted to evaluate the effect of sulphate only and the combined effect of sulphate and chloride ions in an alkaline media on steel. Findings -It was found that sulphate ions could cause corrosion of steel in alkaline media. The severity of the attack increased with increasing sulphate ion concentrations, as well as with combinations of sulphate and chloride ions. The pH 12 conditions seem to show much more critical attack with evidence of pitting corrosion as compared to uniform corrosion for test conditions at a pH of 9. The attempt to inhibit the observed corrosion of steel exposed to the corrosive high alkaline media containing sulphate ions on their own and in combination of chloride ions by laser surface treatment proved to be successful. Originality/value -The research undertaken here adds to the body of knowledge relating to the effect of sulphate ions on reinforcing steel corrosion in highly alkaline media. Most literature points out that sulphate ions on their own do not have a corrosive effect, but rather, a passivating effect!

Impact of Soil Composition and Electrochemistry on Corrosion of Rock-cut Slope Nets along Railway Lines in China

“…Chloride ion and sulfate radical are the major ingredients of soluble salt, and can directly accelerate the cavitation of metal. Research reveals that corrosion weight loss of carbon steel in alkaline soil is almost in direct proportion to the addition of chloride ion and sulfate ion 56 57 . Researchers such as Lee found that SO 4 2− could hinder the generation of corrosion, but boost the development of corrosion pits that have been formed 58 .…”

Corrosion Activity of Carbon Steel B450C and Stainless Steel SS430 Exposed to Extract Solution of a Supersulfated Cement

“…Reported results [54] have suggested that in chloride-sulphate solutions (pH = 8), the mild steel did not passivate, and the corrosion resistance significantly decreased; however, the corrosion rate of the stainless steel AISI 315L was twice as low, presenting pitting corrosion influenced by the chloride ions, although this steel was in a passive state. Mass loss and electrochemical tests [55] revealed that sulphate ions could cause the corrosion of reinforcing steel in alkaline media (pH 9-12) and in the presence of chloride ions the attack is more severe, with evidence of pitting corrosion.…”

Pore Solution Chemistry of Calcium Sulfoaluminate Cement and Its Effects on Steel Passivation

“…Several papers have been published on the effects of SO 4 2− , but they neglect the influence of hydroxyl concentrations [10][11][12][13][14]. From the evolution of the corrosion potential in Figure 5, it is evident that the depassivation caused by SO 4 2− is sensitive to alkalinity.…”

“…Alhozaimy [9] reported that, with the addition of Ca(OH) 2 in a solution of 0.1 M NaOH and 0.175 M KOH, the constitution of passive film changed, and the charge transfer resistance also increased noticeably. Additionally, SO 4 2− may also affect the condition of the steel bar, as indicated by Abd El Hallem and Premlall [10,11], who claimed that SO 4 2− can cause more severe corrosion than Cl − . However, this conclusion was not no experimental evidence supports this point.…”