Box-behnken Design to Enhance the Corrosion Resistance of Plasma Sprayed Fe-based Amorphous Coating

Abstract Fe48Cr15Mo14C15B6Y2 (at. %) amorphous coatings under various spraying parameters were deposited on Q235 steel by atmospheric plasma spraying. Passive film thickness was estimated by power-law formula proposed by Hirschorn to investigate the corrosion properties of passive film on the coating surface. Box-behnken design (BBD) in combination with response surface methodology (RSM) was utilized to gain the thickest passive film (about 1.60 nm) in 3.5 wt. % NaCl solution. XPS results indicated that passive film formed on the optimal coating comprised of Fe, Cr and Mo oxide species and certain amount of bounded water. Mott-Schottky curve further confirmed an enhanced corrosion resistance of the optimal coating due to a low carrier density under the magnitude of 1018 cm-3. The surface morphology after 20 days immersion suggested that no corrosion products were observed on the optimal coating surface and the passive film retained its stability to protect the metal substrate effectively.