Nitrite corrosion inhibition in chloride-rich electrolytes correlated to the electrical properties of surface films on carbon steel

M.A. FRONTINI; W. H. SCHREINER; VAZQUEZ M.; M. B. VALCARCE

CONSTRUCTION AND BUILDING MATERIALS

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 2019 vol. 227

0950-0618

The electronic properties and the composition of surface films grown in pore simulating solutions arestudied using various electrochemical and surface techniques and then correlated to the inhibiting efficiencyof nitrite ions in chloride-rich alkaline solutions. In nitrite-free and chloride-rich solutions, theexternal layer of the surface film is porous, defective and rich in Fe(III). Instead, when nitrite and chlorideions are simultaneously present, the Fe(II) content increases and the film becomes thicker, ordered andmore protective. In the absence of nitrite ions, chloride ions induce high donor densities that correlate toa high susceptibility to localized corrosion. In contrast, the donor density decreases noticeably whennitrites and chlorides are both present and also increases with ageing time, reaching values comparableto those calculated for uncontaminated solutions.