Analysis Of Corrosion Mechanisms Research Articles

Study on test of free and total SO42- in cement-based materials subjected to sulfate attack by conductivity titration

It is necessary to accurately, efficiently, and economically test SO42- in cementitious materials subjected to sulfate attack for the calculation of diffusion coefficient, estimating damage degree and analysis of corrosion mechanism. In this study, the test of free and total SO42- in cementitious materials was investigated by conductivity titration. The results show that the key to test SO42- by conductivity titration is removement of the influential ions such as H+ and OH- with higher molar conductivity. In the test of free SO42-, HCl or CO2 can be used to eliminate the effect of OH- or OH- and Ca2+. In the test of total SO42-, the combination of Ag2O with Ag2CO3 or the combination of Ag2O with CO2 can be used to eliminate the effect of H+, Cl-, and Ca2+ where Ag2O and CO2 is more applicable to eliminate influential ions because CO2 is easily controlled by CO2 generator. The ultrasonic can be used to clean the AgCl attached to the surface of Ag2O to increase the hydrolysis reaction of Ag2O. To eliminate the effect of reaction between Ag+ from hydrolysis reaction of Ag2O and Cl- from the conventional titrant of BaCl2 on titration endpoint, the Ba(NO3)2 is chosen as a new titrant.

Pitting Corrosion of S13Cr Tubing in a Gas Field: A Failure Case and Corrosion Mechanism Analysis

Pitting Corrosion of S13Cr Tubing in a Gas Field: A Failure Case and Corrosion Mechanism Analysis

Theoretical prediction of acid dew point and safe operating temperature of heat exchangers for coal-fired power plants

Research on acid dew point and condensation process of flue gas is necessary for making full use of waste heat in coal-fired boilers and reducing low temperature corrosion of heat exchangers. The iterative calculation of acid condensation is studied with consideration of both the gas-liquid equilibrium effect and multi-component diffusion effect. Furthermore, based on the thermodynamic data of water vapor and sulfuric acid vapor, the iterative calculation model of the acid dew point is proposed. The iteration result shows great consistency with the experimental data, and with the maximum and minimum deviation being around 2.68°C and 2.07°C, respectively. The single-factor and orthogonal calculations are analyzed to obtain the effects of temperature, acid vapor content and water vapor content on the acid condensation. In addition, the safe operating temperature of heat exchanger is suggested based on the analysis of corrosion mechanism and acid condensation calculation results. The lowest temperature of heat exchanger is recommended above 80°C in the practical application of waste heat utilization in coal-fired boilers.

Effects of Aging Treatment and SiCp Addition on Compressive Performance and Corrosion Behavior of Mg-10Zn-0.6Zr Alloy

This paper addresses the collective effects of aging treatment and addition of SiC particles (SiCp) on both the compression performance and corrosion behavior of Mg-10Zn-0.6Zr alloy through experimental study. The results indicate that aging treatment at 180°C for 18h while adding SiCp can improve both the compressive strength and the corrosion rate of Mg-10Zn-0.6Zr alloy. The microstructure analysis and corrosion mechanism analysis justify the effects observed. Specifically, the improvement of compressive strength is due to the fine grain strengthening and second phase strengthening. Acceleration of corrosion is attributed to two factors. The first is the precipitation of the second phase after aging treatment. The second is the morphological changes of corrosion products resulted from aging treatment and addition of SiCp.

Study of the Additional Anti-Corrosion Measures of Bridge Pier Caps Concrete in Beijing-Shanghai High Speed Railway

Based on the analysis of corrosion mechanism, combining with the characteristics of bridge structure, aiming at the existence of corrosive medium and complex physical environment, such as the freezing thawing, corrosion and chlorine salt as well as dry wet, freeze-thaw cycle [, This paper expounds the research and construction practice of the additional anti-corrosion measures of bridge pier caps concrete in Beijing-shanghai high speed railway. It has a certain guiding significance to the similar Bridges in corrosion protection construction.

High corrosion resistance multilayer nickel coatings on AZ91D magnesium alloys

The multilayer coatings consisting of electroless Ni–P, Ni–P–ZrO2 and electroplating Ni coatings were investigated. The surface and cross-section morphologies of coatings were observed with SEM. The microstructures were analysed by XRD. The corrosion resistance was evaluated by potentiodynamic polarisation curves and salt spray tests. The results showed that the electroplating Ni coating was crystal structure, whereas the electroless Ni–P and Ni–P–ZrO2 coatings displayed amorphous characteristic. The electroplating Ni coating exhibited more positive corrosion potential Ecorr and lower corrosion current density Icorr than that of electroless Ni–P and Ni–P–ZrO2 coatings. The samples covered with multilayer coatings of Ni–P–ZrO2/Ni/Ni–P (from substrate to surface) indicated the best corrosion resistance among six samples, and the salt spray tests were carried out for more than 1000 h. According to the analysis of corrosion mechanism, the upper Ni–P layer served as sacrificial protection anode due to its more negative corrosion potential Ecorr in comparison with the middle electroplating Ni layer. When the upper Ni–P layer was consumed, the middle Ni layer went to prevent from corroding. Until the corrosion pits penetrated all of the protective coatings, the substrate of magnesium alloys was destroyed completely.