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Cyclic voltametry and potentiodynamic single sweep techniques are used to study the electrochemical behaviour of lead in Na₂CO₃ solutions containing various concentrations of ClO₄^‐ as aggressive anion. The effects of different concentrations, in terms of destruction of passivity and initiation of pitting corrosion, were monitored with reference to the change in integrated anodic charge. It was found that Δq_a (taken as a measure of the extent of pitting) varies linearly with log C_ClO4‐. The pitting corrosion potential, E_pitting, varies with log C_ClO4‐ according to sigmoidal curves. These curves are explained on the basis of formation of passive, active and continuously propagating pits. Additions of aliphatic amines shift the pitting corrosion potential, E_pitting, into the noble (positive) direction, indicating the inhibition action of the added amines on the pitting attack. E_pitting varies with the logarithm of the inhibitor concentration according to: E_pitting = a + b log C_inh. The inhibition of pitting corrosion by the aliphatic amines is assumed to be due to either competitive adsorption between the CO₃^2– with ClO₄^‐ anions, and/or the chemisorption of the amine on the metal with the formation of a metal‐nitrogen coordination bond. The efficiency of these compounds as pitting corrosion inhibitors increases with the increase in the chain length of the alkyl group.

PITTING CORROSION generally takes the form of localised corrosive attack at closely defined points, whose area constitutes only a minute part of the total surface of the steel. The considerably higher rate at which the steel goes into solution at these points causes the cavities to grow in depth, and may ultimately result in perforation. Fig. 1. The rate of pitting corrosion is largely determined by the proportion of the total cathodic to the total anodic area. The anodic current and the cathodic current flowing in the corrosion cell are equal.

The relatively complex corrosion mechanism of aluminium has been studied by several authors. Corrosion of aluminium occurs only when the metal protective oxide layer is damaged and when the repair mechanism is prevented by chemical dissolution. Polarization methods have been extensively used to investigate the mechanism of localised corrosion and processes that lead to localised corrosion. The potential‐pH diagrams are shown in Fig. 1A. In using potentiostatic techniques, the potential is controlled and current is determined as the independent variable. Potentiostatic and potentiody‐namic techniques have been applied by several authors to study the corrosion of aluminium in different environment. Both anodic and cathodic polarization curves have been used to interpret the kinetics of pitting corrosion of aluminium in chloride containing environments. Both the anodic and cathodic process are complex and the interpretation of the anodic and cathodic polarization curves of aluminium is often tedious. The situation arises partly from the fact that the role of film formation on the kinetics of corrosion is not clearly understood. Previously there is not established mechanisms of initiation and propagation of pits in aluminium and its alloys. Several parameters such as pitting potential, breakdown potential, active passive transition potential, related to the pitting process of aluminium, are full of controversy. Numerous references on the above can be found in literature).

In this paper, the authors aim to study the effect of hydrogen on the pitting corrosion behavior of Incoloy 825, a commonly used material for heat exchanger tubes in hydrogenated heat exchangers.

The pitting initiation and propagation behaviors were investigated by electrochemical and chemical immersion experiments and observed and analyzed by scanning electron microscope and energy dispersive spectrometer methods.

The results show that hydrogen significantly affects the electrochemical behavior of Incoloy 825; the self-corrosion potential decreased from −197 mV before hydrogen charging to −263 mV, −270 mV and −657 mV after hydrogen charging, and the corrosion current density increased from 0.049 µA/cm² before hydrogen charging to 2.490 µA/cm², 2.560 µA/cm² and 2.780 µA/cm² after hydrogen charging. The pitting susceptibility of the material increases.

Hydrogen is enriched on the precipitate, and the pitting corrosion also initiates at that location. The synergistic effect of hydrogen and precipitate destroys the passive film on the metal surface and promotes pitting initiation.

This paper aims to expand the application area of Inconel 718 alloy in marine environment, the sensitivity of pitting corrosion should be analyzed and discussed, especially the effect of block carbides.

Effect of carbides on the sensitivity of pitting corrosion for Inconel 718 alloy was carried out at 30°C in 3.5% NaCl solution using dynamic electrochemical impedance spectroscopy and anodic polarization techniques. In addition, the initiation of pitting corrosion was investigated by immersion test in 0.05 M HCl + 6% FeCl₃ solution.

As a result, the precipitation of carbides, as the initiation of pitting corrosion, increased pitting corrosion susceptibility, especially the block carbides could lead to deep-spalling. Within that process, temperature and potential acted as the main controlling factors, and the effect of the latter was more distinct.

The initiation of pitting corrosion was revealed by the immersion test. The mechanism of pitting corrosion was analyzed and discussed.

Water can alter the performance of modern gear lubricants by influencing the flank load carrying capacity of gears significantly. The purpose of this paper is to investigate the influence of water contaminations in different kinds of base oils on the micro-pitting and wear performance of case carburized gears.

Concerning micro-pitting and wear, tests, based mostly on the following standardized tests, are performed on a Forschungsstelle fuer zahnraeder und getriebebau (FZG)-back-to-back gear test rig: micro-pitting short test Graufleckenkurztest (GFKT) according to DGMK 575 (screening test), micro-pitting test Graufleckentest (GT) according to FVA 54/7 (load stage test and endurance test) and Slow-speed wear test according to DGMK 377. To investigate the effect of water on the gear load carrying capacity dependent on different types of base oils, two polyglycol oils (PG1 and PG2), a polyalphaolefin oil, a mineral oil and an ester oil E are used. Each of these oils are common wind turbine gear oils with a viscosity ISO VG-220. Additionally, a manual transmission fluid with a viscosity of society of automotive engineers (SAE) 75W-85 is tested.

Considering the micro-pitting and wear performance, a significant decrease caused by water contaminations could not be detected. Regarding pitting damages, a generally negative influence was observed. This influence was differently distinctive for different base oil types. Especially non-polar lubricants seem to be affected negatively. The documented damages of the tooth flanks confirm this observation. While typical pitting damages appeared in test runs with polar lubricants, the disruption in test runs with non-polar lubricants was more extensive. Based on the experimental investigations, a general model of the damaging mechanisms of water contaminations in lubricants was derived. It is split into three partitions: interaction lubricant–water (effect of water on the molecular structure of base oils and additives), chemical-material-technological (especially corrosive reactions) and tribological influence (effect of water droplets in the contact zone). It has to be considered that the additive package of lubricants affects the influence of water contaminations on the flank load carrying capacity distinctively. An influence of water on the micro-pitting and wear performance in other than the given lubricants cannot be excluded.

While former research work was focused more on the effects of water in mineral oils, investigations concerning different types of base oils as well as different types of damages were carried out within this research project.

The SiC reinforced Al composite is perhaps the most successful class of metal matrix composites (MMCs) produced to date. They have found widespread application for aerospace, energy, and military purposes, as well as in other industries – for example, they have been used in electronic packaging, aerospace structures, aircraft and internal combustion engine components, and a variety of recreational products. In all these applications, welding plays a vital role. Little attention has been paid to SiC reinforced aluminium matrix composites joined by gas tungsten arc (GTA) welding. The purpose of this paper is to outline the manufacturing method for producing MMCs, GTA welding of MMCs and pitting corrosion analysis of welded MMCs.

This paper focuses upon production and welding of metal matrix composites. The welded composites have been treated at elevated and cryogenic temperatures for experimental studies. Pitting corrosion analysis of welded plates was carried out as per Box Benkehn Design.

From the results, it should be noted that maximum pitting resistance was observed with MMCs containing 10% SiC treated at cryogenic temperature. Corrosion resistance of welded composites treated at elevated temperature was found to be higher than that of as‐welded and at cryogenic temperature treated composites. The pitting potential increases with increase in % SiC to certain level and decreases with further increase in % SiC. Corrosion potential of composites treated at elevated temperature is high compared to other composites. Maximum pitting resistance is observed when the welding current was kept at 175 amps for 10% addition of SiC in LM25 matrix treated at cryogenic temperature.

The paper outlines the manufacturing method for producing MMCs, GTA welding of MMCs and pitting corrosion analysis of welded MMCs. The results obtained may be helpful for the automobile and aerospace industries.

Corrosion is one of the common damage mechanisms in many engineering structures such as marine structures, petroleum pipelines, aerospace and nuclear reactor. However, the service performance of metal materials and structures is gradually degenerating with the increase of service life due to the rapid growth of corrosion damages. Thus, the coupled effects for corrosion damage in reliability analysis should be considered urgently. Then, the purpose of this paper is to develop the corrosion damage physical model and the corresponding reliability analysis methods, which consider the coupled effect of corrosion damage.

A failure physical model, considering the coupled effect of pitting growth, crack and crack propagation, is presented in this paper. Sequentially, the corrosion reliability with respect to pitting physical damage can be investigated. The presented pitting damage physical model is formulated as time-variant performance limit state functions, which include the crack transition, crack growth and fracture failure mechanics. The first-passage failure criterion is used to construct the corrosion reliability framework, involving in the pitting damage model with the increase of service life.

Results demonstrate that the multiplicative dimensional reduction (MDR) method behaves much better than FORM no matter in accuracy or efficiency. The proposed corrosion reliability method is applicable for dealing with the damage failure model of the structural pitting corrosion.

The MDR method is used to calculate the corrosion reliability index of a given structure with fewer function calls. Finally, an aeronautical metal material is used to demonstrate the efficiency and precision of the proposed corrosion reliability method when the failure physical model considering the coupled effects of mechanical stresses and corrosion environment is adopted.

The purpose of this study is to analysis the pitting corrosion on the mechanical behavior of E690 high-strength steel sandwich panel. The pitting corrosion depth and degree of pitting (DOP) damage were used to evaluate the mechanical behaviors such as peak load and specific energy absorption of E690 panel.

The mechanical behavior of quasi-static compression, low-speed impact and three-point bending of E690 panel after pitting corrosion was simulated by ABAQUS nonlinear finite element method.

The quasi-static compression and low-speed impact mechanical properties can be greatly reduced by the pitting corrosion of the panel core, the pitting corrosion of the outer panel shows no obvious effect. The mechanical properties decrease with the increase of the pitting corrosion depth and DOP, and the influence of DOP is greater than that of pitting corrosion depth. The DOP of outer panel has less effect on mechanical properties of three-point bending compared with that of the core. Therefore, the pitting corrosion in the core of panel should be strictly controlled to prevent adverse effects on the mechanical properties of the structure.

To make up for the deficiency of the research on the corrosion behavior of high-strength steel sandwich panel structure, this paper chose E690 high-strength steel panel as the research object, and nonlinear finite element method was adopted to simulate the influence of pitting corrosion coverage area and pitting depth on its mechanical property degradation. The quasi-static compression, low-speed impact and three-point bending mechanical properties of panel with various DOPs and pitting depths were systematic studied.

The purpose of this study was to investigate the pitting resistance and assess the critical pitting temperature (CPT) of a super martensitic stainless steel, 00Cr13Ni5Mo2, made in China, considering especially the difference in the pitting corrosion resistance between the domestic super martensitic stainless steel and an imported one.

Potentiodynamic sweep tests were applied to investigate the effects of four NaCl concentrations (weight per cent) of 1, 3.5, 9 and 17, and four testing temperatures of 30, 50, 75 and 90°C on the pitting resistance of the domestic super martensitic stainless steel in the presence of CO₂. Potentiostatic sweep tests were utilized to determine the CPT. Furthermore, chemical immersion exposures, implemented according to the appropriate standard were used to evaluate the difference in the pitting corrosion resistance between the domestic super martensitic stainless steel and an imported one. In addition, the morphology of pits was analyzed using a scanning electron microscope.

The pitting potential of the domestic super martensitic stainless steel decreased with an increase in NaCl concentration and temperature in the presence of CO₂. The CPT of the domestic super martensitic stainless steel measured by potentiostatic polarization was 41.16°C. Two types of typical corrosion pits, closed pits formed at 35°C and open pits formed at 50°C, were observed. Furthermore, compared to the super martensitic stainless steel made in Japan, the domestic one was better in terms of pitting potential, corrosion rate and the density of the pits, but worse in terms of the depth of the pits, which may result in a risk of corrosion perforation of tubing and casings.

The paper highlights that chloride ions, temperature and the presence of CO₂ play an important role on the pitting resistance of super martensitic stainless steel.