Surface Composition of Stainless Steels during Anodic Dissolution and Passivation Studied by ESCA

Abstract

A molybdenum containing austenitic steel was exposed in hydrochloric acid at various potentials in the active and passive ranges of the alloys. The surface compositions were analyzed by the ESCA technique. The influence of pretreatment by ion bombardment and mechanical polishing on the passivation behavior was investigated. The passive film formed on the surface consists mainly of a mixed Fe‐Cr‐Mo oxide. The average content of Cr3+ in the oxide is about 70%. The inner layers of the oxide product consist mainly of Cr oxide. The Ni content in the oxide is low. The concentration and the chemical state of Mo is potential dependent. At low potentials in the passive range, the four‐valency state is predominant, while at high potentials Mo exists mainly in its six‐valency state. On the surface of the oxide, a layer of hydroxide is present. Chloride ions are incorporated into the passive film. The thickness of the passive film increases with the potential in the passive range from 10 to 15Å. The composition of the metal phase changes during active dissolution. Thus, the alloying elements are enriched on the surface and thereby control the dissolution rate, control overpotentials, and provoke passivation of the alloy.

Investigation of Passive Film Properties and Pitting Resistance of AISI 316 in Aqueous Ethanoic Acid Containing Chloride Ions using Electrochemical Impedance Spectroscopy(EIS)

“…ions. An increase in the thickness of the passive film with increase in Mo content has been reported by Olefjord et al [31]. By the virtue of the alloying elements, there occurs formation of multi-layered passive film on the surface.…”

Influence of ethanol, acidity and chloride concentration on the corrosion resistance of AISI 316L stainless steel

“…For different stainless steels, this potential region was attributed to the increase in the thickness of the oxide film formed in region B. [17][18][19][20] Some works [20][21][22][23][24] considered that the film thickness increased linearly as a function of potential, and consequently the electric field remained constant (at ca. 10 6 -10 7 V cm -1 ) during the film formation process.…”

The corrosion resistance of 316L stainless steel coated with a silane hybrid nanocomposite coating

“…4 As a follow-up of these results, the present work aims at evaluating the structure and corrosion protection performance of silane sol-gel hybrid coatings deposited on austenitic 316L stainless steel. This steel combines properties such as acceptable biocompatibility and excellent mechanical resistance with easy fabrication at low cost, which permits its use in many industrial applications, consumer products and temporary orthopedic devices [32][33].…”