Z. Szklarska-Smialowska

Pitting corrosion of aluminum

This review describes the experiments performed during the last few decades which enhance knowledge of the pitting of aluminum. Specifically, metastable and stable pits, pit chemistry and the effect of intermetallics on pitting are discussed. The properties of metastable alloys and inhibition of Al are also discussed.

Mechanism of pit nucleation by electrical breakdown of the passive film

Abstract Based on the similarity between the electrical breakdown of insulators and the pitting breakdown, the mechanism of the breakdown of passive film of transition metals in a chloride solution is described. It is proposed that nucleation of pits occurs by electrical breakdown, probably by the Zener mechanism. Creation of a very high current locally destroys the passive film and causes the dissolution of the metal forming metastable or stable pits.

The mechanism of stress corrosion cracking of alloy 600 in high temperature water

Abstract The different mechanisms proposed to explain the stress corrosion cracking (SCC) of alloy 600 are briefly reviewed and their validity to explain the influence of the variables and to predict the crack growth rate (CGR) is assessed. It is concluded that several of the proposed models seem to give a fair estimate of the CGR values under certain conditions; it appears that a single mechanism cannot explain in detail the complex alloy 600 SCC. There is a total absence of explanation in the literature of the events leading to the nucleation of cracking. It is suggested that processes controlled by diffusion such as internal oxidation or environmentally assisted creep may establish the length of induction time observed in plants.

Insight into the pitting corrosion behavior of aluminum alloys

Abstract On the basis of the literature data and the current results, a mechanism for the pitting corrosion of Al alloys is proposed. An assumption is made that the transport of Cl− ions through defects in the passive film of aluminum and aluminum alloys is not a rate determining step in pitting. The pit development is controlled by the solubility of the oxidized alloying elements in acid solutions. A very good correlation was found between the pitting potential and the oxidized alloying elements for metastable AlCr, AlZr, AlW and AlZn alloys.

The composition and properties of oxide films on type 304 stainless steel on exposure to lithiated water at 100–350°C

Abstract The oxide films formed on type 304 stainless steel in lithiated water containing dissolved hydrogen were examined at constant temperatures of 100, 150, 200, 250, 300 and 350°C by open circuit potential measurements, Auger electron spectroscopy analyses, semiconductivity measurements and a.c. impedance experiments. Between 150 and 200°C, most of the properties examined were found to change drastically. The steady state open circuit potential was close to that of the reversible hydrogen electrode (RHE), and the measured current density corresponded to the exchange current density of RHE.

Effect of solution composition and electrochemical potential on stress corrosion cracking of X-52 pipeline steel

Abstract Electrochemical measurements and constant extension rate tests (CERT) of cold-worked X-52 carbon steel showed stress corrosion cracking (SCC) can be induced in aqueous sulfate (SO42−), bic...

The kinetics of pit growth on alloy 600 in chloride solutions at high temperatures

Abstract Alloy 600 tube specimens were subjected to corrosion in de-aerated 0.1 M NaCl solution at 100–250°C at applied potentials more positive than the respective pit nucleation potentials, and in de-aerated 200 ppm CuCl 2 solution at 150 and 280°C under open circuit conditions. In NaCl, the pits grew in depth proportionally to t 0.3 , t 0.5 and t 0.7 ( t = time) at 100, 150 and 250°C, respectively. In CuCl 2 at both 150 and 280°C, the pit deepening rate was proportional to t 0.4 . In both the solutions studied, the density of pits observed on the surface of specimens after the same time of corrosion at 100°C was less than at higher temperatures, whereas the pit depth was greater at 100°C than at higher temperatures. The morphology of pits was temperature dependent. The corrosion products accumulated on pit bottoms were enriched in Cr, Ti and S, and impoverished in Fe and Ni.

Susceptibility of medium-strength steels to hydrogen-induced cracking

Abstract Anodic current transients obtained by using the potentiostatic double pulse (PDP) technique for BHS-1, 4037, 1022 QT and 1022 CN steels were analysed with a diffusion-trapping model to determine the hydrogen trapping constant and hydrogen entry fluxes. The BHS-1,4037 and 1022 QT steels exhibited similar high values of trapping constants. Hydrogen entry fluxes were found to be similar for BHS- 1 and 4037 steels; these fluxes are higher than those for 1022 QT and 1022 CN steels. Slow-strain-rate tests showed that the steels with higher values of hydrogen trapping constants and ingress fluxes were more susceptible to hydrogen-induced cracking.

Technical Note: Stress Corrosion Cracking of X-52 Carbon Steel in Dilute Aqueous Solutions

Abstract Slow strain rate tests of cold-worked X-52 carbon (C) steel showed stress corrosion cracking (SCC) could be induced in dilute aqueous sulfate solutions at 50°C. The crack growth rate was of the same order of magnitude reported previously for carbonated solutions. Cracking susceptibility increased for potentials more anodic and more cathodic than the corrosion potential (Ecorr) measured in deaerated solution. Transgranular cracking was observed in pH 6.2 solutions and at Ecorr in pH 8 solutions.

Hydrogen trapping by cold-worked X-52 steel

Abstract The hydrogen trapping by cold-worked (CW) and non-cold-worked (NCW) X-52 steel was evaluated by using the potentiostatic pulse method. The apparent and lattice diffusion coefficients of hydrogen were measured by the permeation technique. On the basis of the results obtained, the susceptibility to hydrogen embrittlement of CW and NCW steels was determined.