The influence of %Cr on the spontaneous passivation of (CoFeNi) (100-x)/3Crx alloys in 0.1 M H2SO4 was investigated. During spontaneous passivation, Cr enrichment occurs due to the selective dissolution of the matrix elements. The quantity of Cr enrichment is relatively constant with Cr content while the total quantity of alloy dissolved decreases with increasing Cr content. Oxygen reduction is the main driving force for the oxidation / passivation of the alloy at open circuit. %Cr has little effect on the kinetics of oxygen reduction. Element resolved polarization curves predict spontaneous passivation by comparing the critical dissolution rate with the cathodic current.