The effects of nano-SiO2 additive on the zinc phosphating of carbon steel

► Nano-SiO2 is helpful for phosphate nucleation and leads to smaller crystals. ► Nano-SiO2 leads to microstructure of the coatings more uniform. ► Nano-SiO2 can substitute the traditional nitrite in phosphating baths. ► The optimal content range of nano-SiO2 is 2-3 g/L.