Explicit microstructural and electrochemical study of value-added carburized mild steel with coconut shell ash and CaCO₃ nanoparticles derived from periwinkle shell

The surface hardening of mild steel by carburization using periwinkle shell nanoparticles (PWSnp) as an energizer and coconut shell ash (CS) as a carburizer was investigated. For the carburization process, PWSnp:CS ratios of 0:0, 1:9, 2:8, and 3:7 were used. The hardness values, corrosion rate, and microstructure of the samples were determined. The results show a 114.1% increase in hardness values and corrosion protection efficiencies of 95.64 and 92.58%, respectively, at 3:7PWSnp:CS in 1 MH₂SO₄ and 35 wt% NaCl. Less corrosion damage was seen in carburized samples because the hard phases provided resistance to the corrosion's destructive activity. It was established that waste periwinkles shell and coconut shell can be used for surface hardening of mild steel.