The addition of copper accelerates the corrosion of steel via impeding biomineralized film formation of Bacillus subtilis in seawater

•Bacillus subtilis can induce biomineralized film on the steel surface.•Bacillus subtilis provides anticorrosion activity via biomineralization.•The addition of Cu to the steel impedes biomineralized film formation.•Cu accelerates corrosion of steel in the medium with Bacillus subtilis. The Bacillus subtilis can induce biomineralized film formation on the surface of steel, which is associated with the positive effects on corrosion. However, the addition of 0.4 wt% Cu to the steel changes the film composition and structures significantly. The biological analyses reveal the mechanism through which Cu influences the metabolism of Bacillus subtilis and carbonate precipitation. The latter plays an important role in protecting corrosion. Furthermore, corrosion pits are larger and more for Cu-steel compared with control steel (free of Cu). This study introduces a new insight for designing an anticorrosion steel in the presence of biomineralized film.