Papers by Keyword: Corrosion Characteristics

Abstract: This paper researches law of reinforcement corrosion under chloride environment based on method the simulated accelerated test. Test the self-corrosion current density and electrode potential quantitative index of concrete reinforcement under chloride environment and establish quantitative model of corrosion time and reinforcement corrosion quantity by means of advanced linear polarization method and electrochemical testing method. Corroded reinforcement weight loss ratio under chloride environment is detected in physical way, combined with reinforcement corrosion layer microstructure and composition characteristics detected by scanning electron microscope. Both of the above deeply reveals corrosion mechanism and corrosion characteristics of the reinforcement. Corrosion rate theoretical model and statistical model have been revised. The research results prove that reinforcement corrosion rate has increased by an average of 4-5 times under chloride environment, weight loss ratio has increased by 15% compared with that under no-chloride environment, and due to chlorine’s effect, partial and uneven corrosion rust layer appears on surface of the reinforcement, which will be the direct cause of inducing accelerating corrosion of reinforcement at the later stage.

Abstract: This paper presents a probabilistic methodology in evaluating corrosion defect characteristics of carbon steels offshore pipelines. A nonlinear multivariate regression model was selected to describe the correlation among corrosion defect parameters while the least-squares method was used to minimize its residuals. The proposed framework were able to provide better insights on the degree of correlations among corrosion defect parameters, which eventually proven that the interactions among defects are indeed significant.

Abstract: The corrosion characteristics of 2205 duplex stainless steel in high- temperature and high-pressure (HT and HP) environments containing H2S/CO2 are investigated in this paper. After corroded 720 hours in the condition of 3.5 MPa H2S, 3.5 MPa CO2, 205°C, 15% NaCl and a sulfide content of 3g/L, one layer of comparably thick corrosion product are formed on the surface of the specimens. The corrosion products, which are relatively porous, lose its protection to the matrix. Lots of pitting are found on the surface of the steel and intercrystalline fracture and transcrystalline fracture are generated in the bottom of the pitting, which indicates its high sensitivity to stress corrosion crack (SSC). Also, the phenomenon of selective corrosion, a priority corrosion of α phase and minor corrosion or non-corrosion of γ phase, is observed after the corrosion process.

Abstract: The corrosion behaviour of the aluminium alloy, AA6082, processed by equal-channel angular pressing (ECAP) after different passes (route E, room temperature) was studied in comparison to the coarse-grained counterpart. The results of the electrochemical investigations (cyclovoltammetry; electrochemical impedance spectroscopy, EIS) are presented in correlation with the microstructure before and after the corrosion examinations. Both, chemical (precipitations, phases) and physical (dislocations, high-angle grain boundaries, grain size, low-angle grain boundaries) inhomogeneities characterize the microstructure of this commercially used Al-Mg-Si alloy. Results indicate an improved resistance against pitting of the ECAP material expressed by a reduced pitting density of up to 50 % and lower pit depths. EIS measurements and microstructural examinations (scanning electron microscopy, transmission electron microscopy, 3D topography measurement) confirm that ECAP modifies the number, size and distribution of these inhomogeneities, which leads to a more favourable corrosion behaviour.