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6061 aluminum alloy is a material that is widely used for manufacturing aircraft. Boron-sulfuric acid anodization is often used in the surface treatment of aluminum alloy to improve the corrosion resistance of the alloy in an outdoor atmosphere. However, few studies have been conducted on the galvanic corrosion of an anodized 6061 aluminum alloy coupled with high strength structural steel in an industrial-marine atmospheric environment. In this work, the outdoor atmospheric exposure test of an anodized 6061 aluminum alloy coupled with 30CrMnSiNi2A steel of different surfaces was conducted in an industrial-marine atmospheric environment. The corrosion behavior and mechanism of the anodized 6061 aluminum alloy coupled with steel were investigated by means of electrochemical measurement, corrosion product analysis, mechanical property testing, fracture analysis, and other measurements. After a one-year exposure test, the values of strength σb and elongation δ of the anodized 6061 aluminum alloy coupled with Cd-Ti plated 30CrMnSiNi2A steel decrease by 6.45% and 4.39%, respectively and have the lowest decline rate compared with the most serious decline rates of 10% and 62.28%, respectively, for the anodized 6061 coupled with naked 30CrMnSiNi2A steel and the moderate decline rates of 6.77% and 10.74%, respectively, for the uncoupled samples. The intergranular corrosion and pitting on the surface of anodized 6061 aluminum alloy result in a significant decrease in the mechanical property, with the deepest crack of intergranular corrosion reaching 150 μm. The sulfide in Qingdao atmosphere not only corrodes the surface of the samples to form aluminum sulfate but also permeates into the grain boundary to promote intergranular corrosion.

The atmospheric corrosion of a metal under a thin electrolyte layer is caused due to the adsorption of the thin electrolyte layer on metal surfaces. As the electrolyte layer is considerably thin, the application of a traditional three-electrode system is considerably difficult; therefore, localized electrochemical technologies are of great use in this field. Herein, different localized electrochemical techniques for atmospheric corrosion under a thin liquid film were discussed. In particular, the applications of scanning Kelvin probe microscopy, wire-beam electrodes, and micro-droplet electrodes were introduced and comprehensively explained. In addition, the key parameters of the tests, which show the relation between thin film/droplet size and corrosion kinetics, were summarized. Furthermore, the issues that currently exist in this field and the potential for improvement was proposed in this research.

Microorganisms and their characteristic metabolisms seriously affect the service performance and service life of materials. To date, most studies have concentrated on the bacterial corrosion of materials and comparatively few have focused on the corrosion behavior and mechanisms fungi exhibit in atmospheric environments. Many fungi exist in the atmosphere and their activities significantly influence the corrosion of metals and coatings. In this paper, the relationship was reviewed between the biochemical characteristics of fungi and the corrosion behaviors of these materials, the effects of fungal corrosion behavior were discussed on metal and coating materials in atmospheric environments, and the mechanism of fungal corrosion was described. By contrasting the features of two types of corrosion, It was found that fungal corrosion mainly differ from bacterial corrosion with respect to their respective metabolites. Currently, most fungal corrosion research has been limited to phenomenal description and corrosion product analysis and has lacked any quantitative characterization of fungal metabolism and corrosion kinetics, which merits greater emphasis in future research.

The stress corrosion cracking of 2024-T351 aluminum alloy was investigated by finite element simulation analysis, scanning electron microscopy/energy dispersive spectrometry, and X-ray photoelectron spectroscopy through SO2 mixed salt spray test. Results indicate that stress corrosion cracking initiates preferentially at the region of stress concentration of the C-ring top for 2024-T351 aluminum alloy. The morphologies of loose corrosion products change from fine rod-like and flocculent to plate-like. Secondary cracks form in the internal corrosion crack after 6 h, when the corrosion time increases to 480 h, and the fractures and cracks in the surface of the C-ring side penetrate the whole sample. The C-ring sample completely breaks after 720 h. The opening crack propagation is a mixed mode of transgranular and intergranular, while the main cracks extend along the normal of the C-ring and the secondary cracks extend mainly along the grain boundaries.

Based on the analysis of aging behavior of ethylene propylene diene rubber(EPDM) and the mechanism of action of climate on EPDM,the aging data of EPDM exposed for 3 years in 11 typical material weathering test stations and the meteorological data there were studied to find out the relation between atmospheric environment and EPDM aging properties. By using the factor analysis and the technique for order preference by similarity to ideal solution(TOPSIS),the comprehensive values of aging properties were gained. With the grey correlation analysis,sever environmental parameters including irradiance,humidity,temperature were found to be the key climate factors which had a significant relation with the degradation of EPDM. Then a BP artificial neural network that connected the climate factors and EPDM aging properties was built. By inputting the meteorological data of cities,the comprehensive values of EPDM aging properties where weathering test had not been performed were predicted and a distribution map of these comprehensive values was draw out. The results show that the aging of EPDM in the south of Guangdong Province,Hainan Island,Taiwan Island,Tibet,and south of Xinjiang are the most serious.

A detection platform of coating failure processes was designed and constructed on the basis of laser electronic speckle pattern interferometry(ESPI). In situ,real-time and dynamic speckle interference fringes were observed and optimized without destroying the coating. An image of coating failure information was acquired by subtracting the zero moment stripe from the in situ and realtime stripes observed and binarizing the results. An experiment of the epoxy color paint/carbon steel system demonstrated the validity of ESPI. According to the ESPI image change,the immersion process of the epoxy color paint coating was divided into three stages:no spots in the initial stage,several blurry spots in the second stage and many clear spots in the last stage. As a result,we successfully realize the in situ,real-time and dynamic nondestructive testing of the coating interface failure and the microcosmic progress of underfilm metal corrosion.

The corrosion behavior of hot air solder level printed circuit boards(PCB-HASL) and electroless nickel immersion gold printed circuit boards(PCB-ENIG) in salt spray test was studied by electrochemical impedance spectroscopy. The corrosion product morphology,composition and coating failure mechanism were observed by stereo microscopy,scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results show that PCB-HASL and PCB-ENIG suffer severe corrosion in high salt spray environment. Localized corrosion occurs first in the Sn plating layer,and then almost entire surface corrosion occurs,similar to uniform corrosion. PCB-ENIG mainly generates microporous corrosion. In the PCB-HASL corrosion process,Cl- promotes the corrosion of the Sn layer,then a large amount of corrosion product gradually forms and covers the Sn surface,it makes the corrosion rate reduce.In the PCB-ENIG corrosion process,a thin liquid layer containing Cl- electrolyte forms in micropores,and galvanic coupling between gold and nickel constitutes,which accelerates Ni corrosion. The Cu base directly exposes in the adverse environment after Ni suffers serious corrosion,finally leading to electronic component failure.

Based on carbon steel surface corrosion,a study was conducted on multifunction acid water-based surface tolerant coatings. The focus was placed on the effect of antirust components and preparation processes on the coating properties. The barrier property was evaluated and compared with imported counterparts. The results show that when the treatment level of the substrate material surface is St1,the adhesive force of the coatings rises at the beginning and then goes downward as the content of the antirust components keeps increasing. The chelating agent contains active groups which stabilize the substrate surface corrosion,resulting in the adhesion performance of the coatings increasing. The compound rust conversion agent improves the coating adhesive force further by translating the corroded substrate surface complexation. The best preparation process needs to mix at low speed and add the compound rust agent at the end of the steps. The adhesive forces of the coatings on the substrate material surfaces treated at St1 and St3 levels show no difference,and they are larger than 5 MPa. The corrosion resisting properties,resistant to salt water for 1200 h,salt spray for1000 h and ultraviolet aging for 2000 h,are much higher than those of similar imported water-based rust primers. The coatings are suitable for the maintenance of complex steel components in atmospheric environment.

The pitting corrosion of 304 L austenitic stainless steel joints with 308 L austenitic stainless steel as welding sticks was investigated in simulated concrete pore solutions with different chloride ion concentrations by potentiodynamic polarization curves, electrochemical impedance spectroscopy and Mott-Schottky curves. It is found that chloride ions play an important role in the corrosion behavior of the joints. When the chloride ion concentration increases, the corrosion potential, breakdown potential and charge transfer resistance of the joints at three different weld zones, i. e., base metal (BM), weld metal (WM) and heat affected zone (HAZ), in the simulated solutions decrease, but the charge carrier density and the number of pitting sites in the joints increase. In the same simu-lated solution, the weld metal shows a better corrosion resistance, followed by the heat affected zone, and the base metal has the lowest corrosion resistance due to its much lower charge transfer resistance and higher doping content.

Four accelerated weathering tests were carried out on polyurethane coated steels. The apparent properties and electro-chemical characteristics of the coatings were studied to compare the effects of different accelerated weathering tests on the coating fail-ure behavior. It is found that UV exerts the greatest influence on the glossiness of the coatings and the gloss loss reaches up to 85.7% after 32 d aging. The linear polarization resistance decreases rapidly in the early period of the salt spray test and stabilizes in the later period due to the formation of a salt film. In the mixed aging (xenon light aging+salt spray) test, the variation tendency of both gloss loss and linear polarization resistance are similar to those presented in the early period of xenon light aging and similar to those presen-ted in the later period of salt spray test. Moreover, the equivalent circuit of the mixed aging test shows two time constants in the early period, which is consistent with the single xenon light aging test. In the later period, the failure process of the coatings can be mani-fested with three time constants, in which the formation of a salt film is the typical feature.

The initial corrosion behavior of the acrylic polyurethane coating/carbon steel interface in a 3.5% NaCl solution was in-situ investigated by electronic speckle pattern interferometry(ESPI),electrochemical impedance spectroscopy(EIS) and scanning electrochemical microscopy(SECM). The effect of nano-TiO2 on the interfacial behavior was examined. At the beginning stage without macroscopic defects,a tiny change at the interface was successfully detected by ESPI. EIS results could reflect the change of low frequency impendence moduli,which were agreed with the electrochemical morphology obtained by SECM. In other words,the interfacial changing velocity(corrosion initiation rate) of the coating without nano-TiO2 is faster than that of the coating with nano-TiO2,indicating that the addition of nano-TiO2 slows down the corrosion of the acrylic-based polyurethane/carbon steel interface.

Based on ultraviolet (UV) accelerated aging tests, aging processes were tracked to study the effects of nano-TiO2 antiaging agent on the surface aging behaviors and anti-aging ability of ethylene-propylene-diene monomer (EPDM). The anti-aging mechanism was also analyzed by Fourier transform infrared spectroscopy (FT-IR) and UV absorption spectroscopy. When the aging time prolongs, the surfaces of EPDM become rough, the chromatic aberration and the glossiness loss increase, the surface carbonyl index rises, while the rate of UV absorbance declines. FT-IR results demonstrate that with coating SiO2, the photocatalytic degradation reaction of nano-TiO2 is inhibited and the aging process of EPDM is postponed. After adding nano-TiO2 anti-aging agent, the hole density decreases, the chromatic aberration and glossiness loss declines by 0.97 and 22.29%, respectively, the surface carbonyl index descends by 0.06, and the rate of UVabsorbance increases by 3.92%. The anti-aging ability of EPDM enhances.

Electrochemical impedance spectroscopy (EIS) was used to study the corrosion behavior of electroless nickel immersion gold processing printed circuit boards (PCB-ENIG) in a simulated electrolyte solution (0.1 mol. L-1 NaHSO3), and the morphology, composition of corrosion products as well as the failure mechanism of the plating layer were analyzed with the aid of stereo microscopy and scanning electron microscopy (SEM) combined with energy dispersive spectrometry (EDS). It is found that the corrosion resistance of PCB-ENIG in NaHSO3 solution is relative poor. Partial discolor appears in PCB-ENIG just immersing for 12 h, along with micro-crack generation. The electrolyte can directly erode the Cu substrate through micro-cracks, forming dendritic crystalline products around these micro-cracks, whose main composition should be Cu2S. Continuous generation of these corrosion products results in large transverse shear stress between the Ni intermediate layer and Cu substrate, and eventually bubbling and shedding of the Ni plating layer occur.