Resistance to pitting and chemical composition of passive films of a Fe-17%Cr alloy in chloride-containing acid solution

Journal Article · Sat Oct 01 04:00:00 EDT 1994 · Journal of the Electrochemical Society; (United States)

DOI:https://doi.org/10.1149/1.2059166· OSTI ID:6822384

Yang, W P; Costa, D; Marcus, P ^[1]

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1. Ecole Nationale Superieure de Chimie de Paris (France). Lab. de Physico-Chimie des Surfaces

The resistance to pitting of a Fe-17%Cr alloy in Cl[sup [minus]]-containing solution (0.5M H[sub 2]SO[sub 4] + 0.3M NaCl) and its relationship with the chemical composition of the passive film have been studied by electrochemical and x-ray photoelectron spectroscopy analyses. Aging of the passive film in the acid solution without or with Cl[sup [minus]] (at a potential below the pitting potential) improves the resistance to pitting. The passive films formed in 0.5M H[sub 2]SO[sub 4] (at +500 mV/SHE) have a bilayer structure (hydroxide and oxide) already well developed after 5 min of passivation. The thickness of the passive film ([approximately]26 to 28 [angstrom]) remains constant during polarization. The average cation fraction of chromium in the oxide increases with increasing polarization time (from 35% after 5 min of polarization to 80% after 24 h of polarization). The beneficial effect of aging on the resistance to pitting is attributed to the enhancement of the chromium oxide enrichment at the film/alloy interface. The passive films exposed to Cl[sup [minus]] or formed in Cl[sup [minus]]-containing solution (0.3M NaCl) have similar composition and thickness as the films formed in Cl[sup [minus]]-free solution, but they contain Cl[sup [minus]]. The Cl[sup [minus]] ions are located mainly in the hydroxide layer ([approximately]0.016 mol [center dot] cm[sup [minus]3]). A very small amount of Cl[sup [minus]] is found in the inner oxide layer.

• OSTI ID: 6822384
• Journal Information: Journal of the Electrochemical Society; (United States), Journal Name: Journal of the Electrochemical Society; (United States) Vol. 141:10; ISSN JESOAN; ISSN 0013-4651
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
ALKALI METAL COMPOUNDS
ALLOYS
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHLORIDES
CHLORINE COMPOUNDS
CHROMIUM ALLOYS
CHROMIUM COMPOUNDS
CHROMIUM OXIDES
CHROMIUM STEELS
COATINGS
CORROSION
CORROSION RESISTANCE
HALIDES
HALOGEN COMPOUNDS
HIGH ALLOY STEELS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
IRON ALLOYS
IRON BASE ALLOYS
IRON COMPOUNDS
IRON OXIDES
METALLURGICAL EFFECTS
OXIDES
OXYGEN COMPOUNDS
PASSIVATION
PITTING CORROSION
PROTECTIVE COATINGS
SODIUM CHLORIDES
SODIUM COMPOUNDS
STAINLESS STEELS
STEELS
SULFURIC ACID
TRANSITION ELEMENT COMPOUNDS