Effect of steel substrate for phosphate treatment: An option to simulate TMT rebar surface

Phosphate coatings have been obtained on three steel substrates: (i) ferritic-pearlitic (F-P), (ii) tempered martensitic (T-M) and (iii) tempered martensitic containing oxide scale (T-M-O) to simulate TMT rebar surfaces which are extensively used for concrete structure. Thinnest coating, constituting of coarse structure and hopeite as the principle phosphate was obtained on F-P steel substrate where as thickest coating, constituting of acicular structure and spencerite as the principle phosphate was obtained on T-M-O steel substrate. Oxide scale on the T-M-O steel substrate acted as catalyst for phosphate reaction. The phosphate coated F-P steel substrate showed better performance against corrosion and bond strength with concrete structure.