The atmospheric corrosion behaviour of 30CrMnSiA high-strength steel exposed in rural, industrial and marine atmosphere environments in China for 60 months was investigated in virtue of the weight loss, X-ray diffractometer (XRD), scanning electron microscope (SEM) and grey relational analysis. The results showed that 30CrMnSiA high-strength steel exhibited the highest corrosion susceptibility and the lowest corrosion susceptibility in marine atmosphere environment and rural atmosphere environment, respectively. Lepidocrocite and goethite were found as the major constituents of the rust layer in three types of atmosphere environments, and akaganeite was also detected in marine atmosphere environment. The rust layer exhibited the tendency of flaking away from the substrate and becoming dense in marine atmosphere environment and rural atmosphere environment, respectively. Grey relational analysis demonstrated that, among a variety of environmental factors, the airborne sea-salt was the primary factor influencing the atmospheric corrosion of 30CrMnSiA high-strength steel. GRAPHICAL ABSTRACT

On aluminum alloys of grades 1060, 2024 and 7075, regular and highly uniform oxide films were formed by anodic oxidation. Anodizing was carried out at a constant pressure in a phosphoric acid solution of various concentrations. Using scanning electron microscopy (SEM) and X-ray diffraction (XRD), the optimal characteristics of the method of anodic oxidation for forming uniform oxide films on aluminum alloys were determined: anodic oxidation time, temperature, voltage and the concentration of H₃PO₄. It was found that, in the process of anodizing, the films have gone through four stages: a non-porosity stage, a mixed stage, an ordered porosity stage and a disordered porosity stage.

Interstitial free steels with various grain sizes and textures were prepared by cold-rolling followed by an annealing process. The effect of grain size, crystallographic orientations and stored energy on corrosion behavior of interstitial free steel was investigated. It was found that the deformed microstructure and dislocation boundaries were consumed by recrystallizing grains during annealing. The average grain size increase ranging from 0.61 μm to 11 μm and the volume fraction of recrystallized grains was about 96% after annealing for 64 h; meanwhile, the γ fiber was the dominated recrystallized texture component. The stored energy gradually decreased due to the reduction in dislocation density by annealing. The potentiodynamic polarization and Nyquist plots show that the corrosion potential exhibits a more positive shift and depressed capacitive semicircle radius increase with rising annealing time. The 64 h annealed specimens had the biggest depressed semicircle in the Nyquist plots and the highest positive corrosion potential, which indicates the enhancement of corrosion resistance. Such an improvement of corrosion resistance is attributed to the increase in the volume fraction of the γ fiber and decrease in the stored energy.