The corrosion troubles of facilities related with heat recovery system in sulfuric acid production industry were characterized in terms of the effect of temperature and concentration of sulfuric acids on the corrosion behavior of stainless steels and alloys, especially the corrosion performance of metallic materials in concentrated sulfuric acids at temperatures above 200 ℃. The article also presented the concept and the function of the so called “corrosion index”, “effect of alloying elements” and “iso-corrosion rate diagram” of stainless steels in detail, which were then recommended to be the suitable reference for materials selection for the heat recovery system in sulfuric acid production.

In this paper, the degradation process and the relevant mechanism of anti-corrosion coatings with and without artificial defects in water containing environments were summarized. The factors affecting the cathodic delamination were discussed, the mechanism of cathodic delamination and blistering were elaborated.

The microstructure of 7B04 aluminum alloy after T6 heat treatment was characterized by transmission electron microscopy (TEM) and its influence on corrosion behavior was studied by means of marine atmospheric exposure test and electrochemical analysis. The results showed that after T6 peak value aging treatment, MgZn² in the alloy precipitates as chain along grain boundaries, and grains of the alloy were obviously deformed and prefrentialy oriented along the rolling direction, which might be fovour to intergranular corrosion; the open circuit potential (OCP) and pitting potential of the alloy is low; the corrosion resistance is poor in marine atmosphere; the corrosion behavior of the alloy seems to be an evolution process of pitting corrosion-intergranular corrosion-exfoliation corrosion, which leads to significant degradation of mechanical property.

The corrosion behavior of LY12CZ aluminum alloy in exfoliation corrosion (EXCO)solution is studied with the accelerated corrosion test. Binary image technology is applied to the corrosion image processing. The corrosion area and the number of corrosion pits are calculated by image processing technique. Test results quantitatively show that the corrosion process of LY12CZ aluminum alloy corrosion in EXCO is pitting corrosion at first then intergranular corrosion and exfoliation corrosion at last. In the early stage of evolution of corrosion process, pitting corrosion rate increased slowly, and the number of corrosion pits increased significantly. As time increases, the small pits were connected each other to form big pits, pitting corrosion area became larger, corrosion became more serious and corrosion morphology became complicated.

The electrochemical corrosion behavior of a composite coating of Al-rich epoxy/Zn-Al galvanizing for Q235 steel was studied in 5%NaCl solution using open-circuit potential monitoring, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and neutral salt spray test. The results indicated that the corrosion performance of the coating during immersion may be presented as three stages. At the initial stage, the Al-rich epoxy top layer prevented corrosive species from attacking. In the middle stage, the Zn-Al galvanizing exhibited electrochemical protection for the substrate. For the third stage, the barrier protection of corrosion products predominated. The neutral salt spray test showed that the composite coating exhibits obviously better anticorrosion performance than the passivated Zn-Al galvanizing.

The corrosion behavior of Q345 steel in five typical soil saturated solutions in Fushun region was investigated by indoor buried corrosion test and electrochemical measurement technology in this paper. The results showed that the corrosion rate of Q345 steel in respective soils was ranked from big to small as an order of Lishi >Lutiankuang>Wanghua>Dongzhou> Gao'ershan. The corrosion rate in Lishi soil was 0.0564mm/a, which was the highest, and it was about seven times as large as that of Gao'ershan soil. The electrochemical measurement results showed that compact and uniform oxide scales formed on Q345 steel in Dongzhou and Gao'ershan soils, whcih prevented the steel from corrosion and expressed the lowest corrosion rate. In Lutiankuang and Wanghua soils, the corrosion products can form quickly, however, they were loose and porous, thus could not protect the steel from further corrosion. The Q345 steel corrosion rate in Lishi soil was the highest, because of the retative high salt content and acidity of the soil accelerated the depolarization of cathodic reaction.

The TiO₂ film was fabricated by electrodeposition technique on 301 stainless steel surface, and the effect of processing parameters on the film structure and anticorrosion performance was systematically studied. The phase constituents and crystallization process of coatings at different temperatures were characterized using X-ray diffraction and TG-DTA analyzer, respectively. In 3.5% NaCl solution, the Tafel curve showed that the film, which was electrodeposited by constant current density of 5 mA/cm² for about 20 min, then annealed at 400 ℃ and hydrothermal post-treated, had the best anticorrosion performance. Cyclic voltammetry curves indicated that in 0.05 mol/L NaOH solution containing different Cl^- concentrations, electrodes of 301 stainless steel with TiO₂ film exhibited corrosion resistance was 2.2 times as high as 301 stainless steel.

Effect of grain size on electrochemical performance was investigated for Al-Zn-Sn-Ga alloy, which has been cold deformed and then heat treated. In the case that the alloy suffered from different degree of deformation, but then heat treatment at the same temperature, the current efficiency firstly increases and then decreases gradually with the increase of grain size. The sample with a moderate grain size (38 μm) has the highest current efficiency. However, as for that the alloy suffered from the same degree of deformation, but then heat treatment at different temperatures, the current efficiency decreases with increasing the grain size. Grain size has no significant effect on the corrosion morphology of Al sacrificial anode.

The relevant theory, design concept, system structure, and functions of subsystems of the newly developed highly accelerated natural environmental system were introduced. The system can comprehensively strengthen the action of the main influencing factors on material corrosion concurrently, such as solar radiation, chloride ion concentration (or other corrosive contaminant in air), temperature, and dry-wet circle etc. Thus the new system can avoid troubles related with unilaterally sthrengthening single or several factors in some existing accelerated natural environmental test technologies. A concept of surface wetness was put forward and a kind of surface wetness sensor was developed, which was applied for intelligent control and optimal strengthening of dry-wet circle to enhance the acceleration efficiency. Exposure tests were comparatively carried out with the new developed system, on far sea exposure site (350 meters to the sea) and on marine platform. Then the corrosion products were characterized. The results showed that incomparison with far sea exposure site, the corrosion rate of steel, aluminum, copper and zinc is multiplied to 11.8, 11.5, 9.3, and 3.7 respectively; The acceleration effect is much significant for coatings, such as the degradation rate for tensile strength of PE and PVC is multiplied to 1.3 and 1.1 respectively. Whilst, the corrosion rate of metals on marine platform is about a half of that at far sea exposure site. Finally the composition and phase constituents of corrosion products of the samples tested in the system is the same as traditional outdoor exposure ones. It was concluded that the new developed system is suitable for fast evaluation of atmospheric corrosion resistance of materials such as metal, coating, plastic, and their workpieces.

The process “corrosion on the ground + fatigue in the air” for aircraft structures was simulated and physical nature of method of so called corrosion-affected cofficient was analyzed. Therewith, the equivalent fatigue damage caused by corrosion was calculated. Afterwards, a new model for predicting aircraft metal structure residual life is proposed in consideration of the coupling-effect between corrosion and fatigue process. Finally, the performance of 2A12-T4 aluminum alloy specimens is studied by means of pre-corrosion and then alternative corrosion-fatigue tests. The results show that the model life is in good agreement with the actual alternative test.

Bursting failure occurred on waterwall tubes of No.5 boiler in a power plant. Macroscopic inspection, chemical analysis, metallurgraphy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were adopted to examine the failed tube. The results indicated that the tube rupture was resulted from localized hydrogen corrosion of the part facing fire. Preventive measures of such failures are put forward.