A Peridynamic Model for Crevice Corrosion Damage

A new peridynamic (PD) model for crevice corrosion damage is introduced and cross-validated with experimental results reported in the literature. The model defines a simple metal ion concentration-dependent corrosion rate along the metal-electrolyte interface. Crevice problems have ratios of gap-to-length of 1/100 or lower. To increase the computational efficiency when having a domain with an extreme aspect ratio, the PD formulation with spherical horizons is modified to accommodate arbitrary-shape horizons. The model is validated against experimental results on immersed bolted washers. The PD simulations predict the observed corrosion kinetics, and the deepest corrosion trenches form at a critical distance from the mouth of the crevice. The location of the most severe corrosion attack does not have to be specified as an input. Instead, it results directly from solving the problem with PD. The evolution of crevice corrosion damage is autonomous in PD, and only the geometry, initial, and boundary conditions control the evolution of the corrosion process.

Effect of Aging Heat Treatment on Corrosion Behavior and Corrosion Kinetics of 17-4PH Stainless Steel in Artificial Saliva

The corrosion behavior of the sintered 17-4PH stainless steel samples aged at different conditions in artificial saliva was studied using the method of electrochemical and weight loss after exposure for various periods of time. The results showed that the samples aged at 480 °C for 1 h exhibited the highest corrosion resistance.The pitting corrosion was predominantly initiated from existing, isolated pores and further accelerated. The corrosion kinetics trend is found to be more consistent with a bimodal function form rather than the classical power-law function.

Evaluation of Glass Coatings with Various Silica Content Corrosion in a 0.5 M HCl Water Solution

Two enamel coatings with a high and a low silica content were prepared on 35CrMo steels via vacuum firing. Their corrosion behavior in a 0.5 M HCl solution including corrosion kinetics, microstructures and electrochemistry performance were studied in comparison with uncoated steels. The results show that catastrophic corrosion occurred for uncoated steels while enamel coatings significantly decreased the corrosion rate. Enamel coatings with a high silica content exhibited the best corrosion resistance against hydrochloric acid due to their highly connected silicate network, which inhibited the leaching process of alkali metals in the acid solution. The corrosion inhibition efficiency for enamel containing a high silica content reached a maximum of 94.3%.

The corrosion kinetics of cordierite-based ZrO2 composites obtained from natural zeolite in dilute HCl acid solution

Being a versatile ceramic, which can be used in various applications, cordierite has always been subject to optimization and research. Nevertheless, the corrosion resistance of the ceramic, synthesized from natural zeolite, has not been widely investigated. In this study, cordierite with 2:2:5 compositions of MgO/Al2O3/SiO2, respectively, was obtained from the natural zeolite. Following sintering at 1250°C for 1 h, of cordierite with 10 and 20% amount of added zirconia (ZrO2), the mechanical properties exhibited proportional amelioration, accompanied by an enhanced homogeneity and reduced microcracks. The corrosion properties were investigated via the weight loss method in 2 vol. % and 5 vol. % HCl acid solutions maintained for up to 480 h at 25, 50, and 75°C. The corrosion kinetics were evaluated from corrosion curves, followed by a calculation of the activation energies of corrosion. The results revealed that ZrO2 addition enhances the resistance, with an optimum observed for the 10% zirconia doped cordierite samples, with varying activation energies between 113 kJ/mol for 5 vol. % HCl acid solution and 119 kJ/mol for 2 vol. % HCl acid solution.