Volume 41, Issue 4

The degradation of materials due to erosion–corrosion occurs on the components that handle particle-laden corrosive slurry. The combined attack of mechanical erosion and corrosion shows increased material loss than the individual action of erosion and corrosion. The synergy accelerates material removal by eroding the corroded surface layer and corroding the surface due to the elimination of the passivating oxide layer by erosion. The synergism of erosion–corrosion is found to be more complex. Further, the coupled effect of mechanical erosion and electrochemical corrosion and the factors influencing erosion–corrosion still needs to be fully investigated. This review aims to provide a general and detailed summary of the interaction between erosion and corrosion of materials for the applications of pump impellers, pipelines for desalination, and oil and gas transportation. Importance is also given to the factors influencing erosion–corrosion, such as erodent particle properties (hardness, size, and shape), slurry properties (particle concentration, pH value, temperature), and flow characteristics (impingement angle, velocity). The various erosion models and the most used apparatus have also been reviewed.

The application of machine learning (ML) to corrosion research has become an important trend in corrosion science in recent years. In this paper, the feature extraction method for corrosion data and the ML algorithms commonly used (including artificial neural networks, support vector machines, ensemble learning and other widely used algorithms) in corrosion field is introduced. Then, the characteristics of different algorithms and their application scenarios in the corrosion prediction are summarized. Finally, the development trend of ML in material corrosion field is prospected.

When most or all of the atoms on a single metal surface are oxidized, corrosion takes place, causing damage to the whole surface. The effects of adsorption and corrosion inhibition on different types of functional groups were studied. A review of these inhibitors based on concentration effect was performed to establish the theoretical results. It has been investigated the effects of 5-(5-(3,5-diaminophenyl)-1,3,4-oxadiazol-2-yl)-N1,N3-di-p-tolylbenzene-1,3-diamine (BATP) on mild steel in 1 M H 2 SO 4 at 30 °C, Levamisole (LMS) and 4-phenylimidazole (PIZ) on copper in 0.5 M H 2 SO 4 , 2-phenyl-1, 4-dihydroquinoxaline (PHQ) on carbon steel in 1.0 M HCl. Based on DFT calculations in the 6–311++G(d,p) basis set in gas and aqueous phases, several quantum chemical parameters were determined to evaluate the array of selected molecules such as HOMO, LUMO, ionization energy, bandgap energy, electronegativity, chemical potential, electrophilicity, nucleophilicity, electron transfer, back-donation energy and Fukui function analysis. The most stable low-energy adsorption configurations of the materials employed in this investigation on the Fe (110) surface were induced using Monte Carlo simulations.

The amperometric biosensor was created using a flat sheet of the Cu-Zn-Al shape memory alloy, with a shiny surface and uniform thickness below 1 mm. The high biocompatibility and a large specific surface area for enzyme loading are evaluated. In vitro biomedical corrosion testing of samples revealed successful immobilization of catalase, which has undergone quasi-reversible electron transfer from the surface and saline solution. A catalase that had been immobilized retained its basic structure and bioactivity and demonstrated a remarkable electrocatalytic response to hydrogen peroxide reduction. The reduction of hydrogen peroxide on the catalase-modified Cu-25.38Zn-3.3Al alloy was investigated using hydrodynamic amperometry in both the absence and presence of l -cysteine and K 2 [B 3 O 3 F 4 OH] inhibitors. Catalytic reduction currents have increased as a result of the gradual increase in hydrogen peroxide concentration. The study on enzyme activity inhibition has shown a lower corrosion rate of catalase-modified bioalloy than the initial sample because inhibitor ions occupy all sites of the immobilized enzyme.

The effect of concentration of an organic imidazoline as inhibitor on internal stress corrosion cracking (SCC) behavior of an API X70 pipeline steel exposed to a brine solution was studied. The SCC process using simultaneously the slow strain rate stress test (SSRT) and electrochemical measurements was performed. Fracture surface analysis and secondary cracking were observed through a scanning electron microscopy (SEM). According to SEM fractography and SSRT results, the steel showed high SCC susceptibility with a brittle fracture and several secondary cracks without addition of inhibitor, whereas the addition of inhibitor to brine solution was effective to increase the SCC resistance of steel at concentrations of inhibitor of 50 and 100 ppm. A further addition of concentration of inhibitor had a negative effect on the mechanical properties of the steel. Electrochemical measurements results are in accordance with the SCC susceptibility, indicating that corrosion inhibitor film suppressed the anodic and cathodic reactions increasing the resistance to SCC until concentration of 100 ppm. Further addition of inhibitor aggravated the localized corrosion due to local desorption of inhibitor molecules. The Hilbert–Huang transform (HHT) analysis revealed the contribution of different corrosion process contained in the electrochemical current noise (ECN) signals at several inhibitor concentrations.

In this work, a scanning Kelvin probe force microscope was used to in-situ visualize distribution of hydrogen atoms at micro-indentation and metallurgical phases contained in a carbon steel. Topographic profiles and Volta potentials of the steel upon various times of hydrogen-charging were measured. The hydrogen atom distribution at the micro-indentation was analyzed. Results demonstrate that the micro-indentation can serve as a preferential site to accumulate hydrogen atoms. Particularly, the vertex of the indention shows the greatest hydrogen atom enrichment, while the indentation bottom possesses a slightly lower hydrogen atom concentration. More hydrogen atoms accumulate in ferrite than in pearlite in the steel.

The priority task of modern aircraft construction is to ensure the reliability of the operation of structures, which depends both on the quality of execution of technological processes during manufacturing and on the corrosion-mechanical durability of welded joints. This work aims to study the influence of contact duration with a corrosive environment on the mechanical strength of the base metal and welded joints of the Al–Mg–Si–Cu alloy, heat-treated in different modes (artificial aging, quenching followed by artificial aging). Corrosion-mechanical tests were carried out under constant axial tensile stress in 3 % NaCl solution for 14 days, followed by determination of the corrosion rate, ultimate strength, and fractographic analysis of the fracture surface. The results showed that the corrosion resistance of the joints is almost equal to the corrosion resistance of the base metal. It was experimentally confirmed that the ultimate strength of the base metal and welded joints decreased after corrosion exposure in a 3 % NaCl solution. This is caused by the embrittlement of the structure and the formation of corrosion defects in the near-surface zone during contact with a corrosive environment, which led to a change like a fracture from ductile to ductile with brittleness.

Silanes are an alternative to replace pretreatments based on Cr(VI) for electrogalvanized steel (ES). As the interaction between the silane and the metal is important to ensure pretreatment efficiency, surface preparation is a critical step. In this sense, the presence of OH groups on the metal surface is essential. In this paper, the surface preparation of ES and a single/double layer application on the corrosion protection afforded by 3-aminopropyltriethoxy silane was studied. The metal surface was cleaned by polishing, electrochemically (employing anodic or cathodic current) or by chemical oxidation. The electrochemical behavior of the cleaned surfaces was analyzed by cyclic voltammetry and electrochemical impedance spectroscopy (EIS). Afterwards, the hydrolyzed silane was applied in a single or double layer. Coatings were characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy, EIS and by exposure to the humidity chamber. Coatings applied on ES cleaned by electrochemical anodic processes or chemical oxidation provided the best protective performance due to a lower surface of zinc exposed to the high humidity environment. Double layer coatings improved protection due to more homogeneous and higher Si content, sealing defects and increasing the thickness of the one-layer protection, enhancing the barrier protection of the silane.