This paper was devoted to the study of changes of electrochemical processes (dissolution, passivation) induced by the plastic strain of a 316L austenitic stainless steel in a chloride acid solution (H2SO4 2 M + NaCl 0.5 M). For this purpose, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods have been used for various plastic strain values. In order to only assess the effect of internal stresses created by various dislocation configurations on the dissolution and passivation processes without considering the surface roughness impact, electrochemical experiments have been carried out after polishing the specimen surface. The obtained results show that the electrochemical parameters (corrosion current, activation current peak, high frequency capacitance) change with the increase of plastic strain with the same behavior as the work hardening phases of the material in relation to dislocation pattern.
The paints are used extensively in various fields, especially for the protection of the oil installations such as the storage reservoirs of crude oil. Reducing possession cost and applying the new hygiene and security standards imply the necessity to deepen the knowledge of the physico-chemical processes of ageing coatings in the first stage and their impact on the corrosion of the substrate.The tests have been carried out on a primer, and on painted steel plates completely immersed in a 3% NaCl solution. The survey of the water absorption and the kinetics deterioration of the paints have been achieved especially by means of electrochemical impedance spectroscopy under the test of salt spray. The barrier weakness of the primer paint, due to the existence of two capacitive loops observed on the Nyquist's diagrams has been put in evidence. While the study of the resistance of the complete system by the test accelerated in the salt spray shows that the system of painting presents a good resistance up to 196 hours, which is equivalent to 8 years of exposure.
The title compound, C12H16N2O2, crystallized from toluene with two independent molecules in the asymmetric unit. The dihedral angles between the amide groups and the benzene ring are 60.87 (11) and 54.08 (11)° in one independent molecule and 60.13 (11) and 64.64 (11) in the other. The crystal structure features weak C—H⋯O hydrogen bonds and C—H⋯π interactions.
Localized corrosion is a serious problem for stainless steel exposed in a chloride solution. In this context, the present work concerns the study of electrochemical behavior of 316 (A and B) and 430 (C and D) stainless steels, where A and C are laboratory steels, while steels B and D were taken from heat exchangers tubes (after 10 years of operation). This study has addressed three different aqueous environments: (1) monoethanolamine (MEA) 15%, (2) natural seawater (NSW), and (3) NaCl 3%, using the technique of potentiodynamic polarization curve complemented by electrochemical impedance spectroscopy (EIS). The obtained experimental electrochemical parameters (E corr , J corr , E r , C d , R tc , and constant phase element) were used to compare the corrosion resistance of the tested steels. As a result, the nobility of these steels in NaCl 3% and in MEA 15% solutions is established in the following order: 316 (A) > 316 (B) > 430 (C) > 430 (D), where E r moves increasingly toward the positive direction, indicating a good protection against corrosion. In addition, the results show that the effect of the electrolyte (aggression) is characterized by increased corrosion potential and a decrease in the passivity domain for all samples. The hierarchy of the nobility of steels A and C in these electrolytes can be determined as follows: MEA 15% > NSW > NaCl 3%.
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