Unraveling the effect of chloride ion on the corrosion product film of Cr-Ni- containing steel in tropical marine atmospheric environment

The effect of Cl - concentration on the corrosion behavior of Cr-containing steel in tropical marine atmospheric environment is systematically studied. Cl - ions affect the adsorption amount of water film, and then affected O 2 diffusion, reducing the generation of NiFeO 4 and Cr(OH) 3 , destroying the electronegativity of inner film, and further weakening the homologous enrichment of Ni, Mo and Cr and intensifying the penetration of Cl - ions. Moreover, the amount of NiO and Cr 2 O 3 decrease due to oxygen reduction, reducing FeOOH nucleation sites, promoting the large-size FeOOH generation and leading to increase the pores in the corrosion product films. • Adding a small amount of Cr to Ni-steel reduces its corrosion rate. • Cr element can promote more NiFe 2 O 4 forming in the inner film and thus more Ni 2+ and Cr 3+ ions are attracted, repelling negatively charged Cl - and effectively shielding the penetration of Cl - . • High Cl - concentration reduces the content of O 2 , inhibiting the formation of NiFe 2 O 4 and Cr(OH) 3 in the inner film, and weakening the density of the corrosion product film.