THE EFFECT OF LASER SURFACE TREATMENT ON THECORROSION OF REBAR IN SULPHATE CONTAINING ALKALINEMEDIA

摘要

The effect of chlorides on rebar corrosion is well documented in the literature.However, few studies have focused attention on the effect of sulphates on thecorrosion of mild steel rebar material in alkaline media. This paper describes theresults of the investigation of mild steel material which is typically used in rebar andwas exposed to alkaline media at a pH of 9 and 12 with varying concentrations ofsulphate ions, as well as combinations of sulphate and chloride ions. An attempt wasmade to inhibit the observed corrosion by laser surface treatment of the mild steelexposed to the corrosive media. Long term mass loss tests and acceleratedelectrochemical tests were conducted to evaluate the effect of sulphate only and incombination with chloride ions in an alkaline media on mild steel (rebar) material. Itwas found that sulphate solutions on their own could cause corrosion of the mildsteel in alkaline media. The severity of the attack increased with increasing sulphateion concentrations, as well as with combinations of sulphate and chloride ions.Extensive mass loss was documented for sulphate concentrations alone, and alsowhen in combination with chloride ions. The pH 12 conditions seem to show muchmore critical attack with evidence of pitting corrosion as compared to uniformcorrosion for test conditions at a pH of 9. The attempt to inhibit the observedcorrosion of the mild steel exposed to the corrosive high alkaline media containingsulphate ions on their own and in combination of chloride ions by laser surfacetreatment proved to be successful.