A nanocrystalline surface layer with average grain size of 77 nm was produced on mild steel through a wire brushing process. Its corrosion behavior was studied in the absence and presence of 3-amino-1,2,4-triazole (3-AT) as corrosion inhibitor. Although the increase in the inhibitor concentration shows a positive effect on inhibition efficiency of micro-and nano-grained surfaces, this effect is more remarkable for the sample with a nanocrystalline surface layer. In addition, in the presence of the optimum concentration of 3-AT, temperature increment has a more negative effect on the sample with a microcrystalline surface layer. The results also revealed that due to enhanced adsorption of 3-AT inhibitor and formation of a protective layer with a high polarization resistance, the inhibition effect of 3-AT increased as the grain size decreased from microcrystalline to nanocrystalline.

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