Stainless Steel In Alkaline Solution Research Articles

Tribocorrosion Behavior and Degradation Mechanism of 316L Stainless Steel in Alkaline Solution: Effect of Tribo-Film

Tribocorrosion Behavior and Degradation Mechanism of 316L Stainless Steel in Alkaline Solution: Effect of Tribo-Film

Electrochemical and XPS analytical investigation of the accelerative effect of bicarbonate/carbonate ions on AISI 304 in alkaline environment

Abstract Passivation behavior and surface chemistry of 304 stainless steel in alkaline solution with different HCO 3 − /CO 3 2– concentrations are studied with a combined electrochemical and XPS analytical investigation. Cathodic and anodic reactions are inhibited and accelerated, respectively, attributed to the depletion of acceptable oxygen and variation of passive film properties. Increasing HCO 3 − /CO 3 2– concentration does not alter the bilayer structure but leads to an intensification in electric field strength and composition changes including enrichment of oxidized Cr, increase of Fe(II)/Fe(III) ratio, and decrease of OH − /O 2– ratio. Meanwhile, the film thickness is reduced and the point defect density is increased due to the enhanced film dissolution. High HCO 3 − /CO 3 2– concentration increases the critical chloride concentration of 304 SS in alkaline solution, attributed to the inhibition of the localized acidification within the pits and suppression of the stable pit development.

Effect of pH on the Electrochemical Behaviour and Passive Film Composition of 316L Stainless Steel

The effect of pH on the electrochemical behaviour and passive film composition of 316L stainless steel in alkaline solutions was studied using electrochemical measurements and a surface analysis method. The critical pH of 12.5 was found for the conversion from pitting corrosion to the oxygen evolution reaction (OER). OER was kinetically faster than pitting corrosion when both reactions could occur, and OER could postpone pitting corrosion. This resulted in pitting being initiated during the reversing scan in the cyclic polarization at the critical pH. According to the X-ray photoelectron spectroscopy analysis, the content of Cr and Mo decreased with pH, while Fe content increased. This induced the degradation of the passive film, which resulted in the higher passive current densities under more alkaline conditions. The selective dissolution of Mo at high pH was found, which demonstrated that the addition of Mo in austenitic stainless steels might not be beneficial to the corrosion resistance of 316L in strong alkaline solutions.

Direct evidence of passive film growth on 316 stainless steel in alkaline solution

Evolution of the oxide films formed on the surface of 316 stainless steel needles during the electrochemical polarization in 0.1M NaOH solution is investigated by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). During the polarization process, the films can grow from ~4nm to dozens of nanometers and are composed of crystalline structures incorporated with amorphous phases. Additionally, Cr (III) species that are formed at low potentials will transform into Cr (VI) species in secondary passive region. Fe element is present as Fe3O4-like spinel oxides while no Fe2O3 is found in the films. The Fe/Cr ratio increases with the increase of applied potential.

Electrochemical and passivation behavior investigation of ferritic stainless steel in simulated concrete pore media.

The applications of stainless steel are one of the most reliable solutions in concrete structures to reduce chloride-induced corrosion problems and increase the structures service life, however, due to high prices of nickel, especially in many civil engineering projects, the austenitic stainless steel is replaced by the ferritic stainless steels. Compared with austenite stainless steel, the ferritic stainless steel is known to be extremely resistant of stress corrosion cracking and other properties. The good corrosion resistance of the stainless steel is due to the formation of passive film. While, there is little literature about the electrochemical and passive behavior of ferritic stainless steel in the concrete environments. So, here, we present the several corrosion testing methods, such as the potentiodynamic measurements, EIS and Mott–Schottky approach, and the surface analysis methods like XPS and AES to display the passivation behavior of 430 ferritic stainless steel in alkaline solution with the presence of chloride ions. These research results illustrated a simple and facile approach for studying the electrochemical and passivation behavior of stainless steel in the concrete pore environments.

The electrochemical behaviour of 2205 duplex stainless steel in alkaline solutions with different pH in the presence of chloride

The electrochemical behaviour of 2205 duplex stainless steel in alkaline solutions with different pH values in the presence of NaCl was evaluated by different techniques: potentiodynamic measurements, electrochemical impedance spectroscopy and capacitance measurements (Mott–Schottky approach). The chemical composition was studied by X-ray photoelectron spectroscopy (XPS). In addition, the site of pitting nucleated preferentially on the duplex stainless steel had been confirmed by scanning electron microscopy (SEM). The results indicated that both the pH and immersion time play important roles in the evolution of the film resistance, charge transfer processes and the occurrence of pitting. The composition of the surface film changes with the pH value. The film formed in the alkaline solution, presenting a bilayer structure, predominantly contained Fe species and Cr-oxide. The NH3/NH4+ species in the passive film are disappeared in the pH 10.5 solution. The pit initiation sites occurred in austenite phase near the γ/δ boundaries or at inclusions. The number and size of the pits increases with the decrease of pH value after long time immersion.

Nickel-free manganese bearing stainless steel in alkaline media—Electrochemistry and surface chemistry

The use of austenitic nickel-containing stainless steels as concrete reinforcement offers excellent corrosion protection for concrete structures in harsh chloride bearing environments but is often limited due to the very high costs of these materials. Manganese bearing nickel-free stainless steels can be a cost-effective alternative for corrosion resistant reinforcements. Little, however, is known about the electrochemistry and even less on surface chemistry of these materials in alkaline media simulating concrete pore solutions. In this work a combined electrochemical ( ocp = open circuit potential) and XPS (X-ray photoelectron spectroscopy) surface analytical investigation on the austenitic manganese bearing DIN 1.4456 (X8CrMnMoN18-18-2) stainless steel immersed into 0.1 M NaOH and more complex alkaline concrete pore solutions was performed. The results show that the passive film composition changes with immersion time, being progressively enriched in chromium oxy-hydroxide becoming similar to the conventional nickel-containing stainless steels. The composition of the metal interface beneath the passive film is strongly depleted in manganese and enriched in iron; chromium has nearly the nominal composition. The results are discussed regarding the film growth mechanism (ageing) of the new nickel-free stainless steel in alkaline solutions compared to traditional austenitic steels. Combining the results from pitting potential measurements with the composition of the passive film and the underlying metal interface, it can be concluded that the resistance against localized corrosion of the new nickel-free stainless steel relies on the strong chromium(III) and molybdenum (VI) oxy-hydroxide enrichment in the passive film.

ChemInform Abstract: Formation and Growth of Hydrous Oxide Film on Stainless Steel in Alkaline Solution by Potential Cycling.

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The formation and growth of hydrous oxide film on stainless steel in alkaline solution by potential cycling

By repetitive potentiodynamic cycling in 1 mol dm −3, NaOH solution a hydrous oxide film was formed on a stainless steel AlSl type 302. For the oxide growth, the optimal sweep rate of 50 mV s −1 between −1.7 and 0.5 V(SCE) was found. The voltammetric data of stainless steel accompanied by those of the 64Fe-36Ni and 80Ni-20Cr binary alloys were used in the elucidation of stainless steel surface oxidation/reduction processes. The two main pairs of hydrous oxide peaks in the cyclic voltammogram of SS 302 belong to the Fe(OH) 2 FeOOH and Ni(OH) 2 NiOOH transitions. By recording the open-circuit potential in 0.1 mol dm −3 sulphuric acid the stability test was carried out. The uncycled electrode reached the active potential of −0.45 V almost immediately. Only one cycle in NaOH solution improved its stability. When the hydrous oxide was grown up to the charge storage capacity of 18 mC cm −2 (expressed by the means of voltammetric charge of anodic Fe(OH) 2 FeOOH transition), the open-circuit potential was still on the positive side after 6 days.

Growth of passivating films on scratched 304L stainless steel in alkaline solution

The kinetics of repassivation of Type 304L austenitic stainless steel in 1.0 M KOH solution have been studied as a function of applied potential. The technique used involves analysis of the current transients that result from rapid mechanical removal of the pre-existing oxide film while the metal is held at constant potential. Two kinetically distinct regions of passive film growth are found, the first occurring at short times when the anodic charge passed is low, and the second occurring at longer times. The kinetics of film growth in both regions are controlled by ion conduction through the film under high electric field.