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1、2 Application of Electrochemical Techniques and Mathematical Simulation in Corrosion and Degradation of Materials Jorge Gonzlez-Snchez, Gabriel Canto, Luis Dzib-Prez and Esteban Garc a-Ochoa Centre for Corrosion Research, Autonomous University of Campeche, Mexico 1. Introduction The tropical climate
2、 prevailing at Yucatan Peninsula in Mexico is characterized by permanently high temperatures and relative humidity with considerable precipitation, at least during part of the year. A high corrosion rate of metals is usually reported for this climate and for marine conditions the corrosion degradati
3、on of infrastructure is an issue of paramount importance. This chapter presents studies about the degradation of some engineering materials, such as austenitic stainless steels (localised corrosion in chloride containing electrolytes) and atmospheric corrosion of copper and nickel-iron alloys from b
4、oth approaches experimental electrochemical tests and theoretical calculations respectively. The evaluation of the corrosion process of stainless steels in chloride containing solutions and atmospheric corrosion of copper in a marine tropical-humid climate are presented and discussed making emphasis
5、 on the electrochemical techniques used. On the other hand, a computational simulation indicated weakening of metal bonds in Fe-Ni (111) surfaces due to interaction with CO after adsorption of this compound. The union weakening observed can be associated with alloy embrittlement by the decohesion me
6、chanism. It is worth mentioning that one important contribution of the Disciplinary research group: Corrosion Science and Engineering of the Centre for Corrosion Research of the Autonomous University of Campeche, MEXICO has been the use for the very first time of the recursive plots methodology for
7、the analysis of current and potential time series from electrochemical noise measurements for studies of localised corrosion. With such approach it was possible to assess changes in the dynamics of the degradation process and to separate the contribution of different phenomena. Novel electrochemical
8、 techniques and advanced methods for data analysis are the base for the understanding of thermodynamic and kinetics aspects involved on the corrosion degradation of engineering materials such as copper, carbon steel and stainless steels. Electrochemical noise (EN), galvanostatic cathodic reduction (
9、CR), scanning reference Recent Researches in Corrosion Evaluation and Protection 28electrode technique (SRET), double loop electrochemical potentiokinetic reactivation method (DLEPR) and electrochemical impedance spectroscopy (EIS) are some of the electrochemical methods used to study the corrosion
10、 degradation process of stainless steels and other engineering metals. The SRET has been used for the quantitative assessment of localized dissolution of AISI 304 stainless steel in natural seawater and in 3.5% NaCl solution at room temperature (25 C) (Gonzlez-Snchez, 2002; Dzib-Prez, 2009). Changes
11、 in the dynamics of intergranular corrosion of AISI 304 stainless steel as a function of the degree of sensitisation (DOS) was evaluated by EN using recurrence plots for the analysis of current time series (Garc a-Ochoa et al., 2009). Also the microstructure dependant short fatigue crack propagation
12、 on AISI 316L SS was distinguished from localised corrosion taking place during corrosion fatigue tests using EN (Acua et al., 2008). The information presented here was divided in two main sections: Atmospheric corrosion and Localised corrosion, followed by a final section of general conclusions. 2.
13、 Atmospheric degradation of engineering alloys 2.1 Atmospheric corrosion of Cu in tropical climates Degradation of engineering alloys due to atmospheric corrosion is the most extended type of metal damage in the world. During many years, several papers have been published in this subject; however, m
14、ost of the research has been made in non-tropical countries and under outdoor conditions. Tropical climate is usual on equatorial and tropical regions and is characterized by high average temperature and relative humidity with considerable precipitation during the major part of the year. Due to thes
15、e conditions a high corrosion rate of metals is usually reported for this type of climate. In coastal regions like the Gulf of Mexico (Yucatan Peninsula), there is a natural source of airborne salinity which plays an important role in determining corrosion aggressivity of these regions (Mendoza & Co
16、rvo, 2000; Cook et al., 2000). The presence of anthropogenic contaminants, particularly sulphur compounds produced at the oil and manufacture industries and transportation have also an important effect on the atmospheric corrosivity of tropical-humid regions. The atmospheric corrosion rate of metals depends mainly on the time of wetness (TOW) and concentration of pollutants; however, if the differences in the corrosion process between outdoor and indoor c
