Abstract
The knowledge of the first-year corrosion losses of metals (K1) in various regions of the world is of great importance in engineering applications. The K1 values are used to determine the categories of atmospheric corrosivity, and K1 is also the main parameter in models for the prediction of long-term corrosion losses of metals. In the absence of experimental values of K1, their values can be predicted on the basis of meteorological and aerochemical parameters of the atmosphere using the dose-response functions (DRF). Currently, the DRFs presented in ISO 9223:2012(E) /1/ standard are used for predicting K1 in any region of the world, along with the unified DRFs /2/ and the new DRFs /3/. The predicted values of corrosion losses (K1pr) of carbon steel, zinc, copper and aluminum obtained by various DRFs for various continental regions of the world are presented. In this work we used the atmosphere corrosivity parameters and experimental data on the corrosion losses of metals for the first year of exposure (K1exp) for the locations of the tests performed under the international UN/ECE program, the MICAT project, and the Russian program. For the first time, a comparative assessment of the reliability of various DRFs is given by comparing the values of K1pr and K1ex using graphical and statistical methods. The statistical indicators of reliability of predicting the corrosion losses of metals are calculated for various categories of atmosphere corrosivity. It is shown that the new dose-response functions offer the highest reliability for all categories of atmosphere corrosivity.
Highlights
The corrosion losses of metals for the first year of exposure (K1) are used to determine the category of atmosphere corrosivity toward each metal [1] and for long-term predictions of corrosion mass losses of metals based on models, including the power and power-linear functions
It is necessary to consider the statistical methods used by different authors for estimating the dose-response functions (DRF) reliability and K1pr accuracy and select at least one of them which is most suitable for practical use
Various statistical indicators characterizing the properties of dose-response functions and the need to use these indicators to estimate the reliability of predicting the corrosion losses of metals have been considered
Summary
The corrosion losses of metals for the first year of exposure (K1) are used to determine the category of atmosphere corrosivity toward each metal [1] and for long-term predictions of corrosion mass losses of metals based on models, including the power and power-linear functions. The variability of climatic and aerochemical atmosphere parameters over the years leads to different K1 values in each test location. Repeated one-year corrosion tests of metals are required to obtain the K1 values corresponding to the average long-term parameters and the level of atmosphere pollution at a given time. Dose-response functions (DRFs) have been developed for estimating K1 at any location. They are based on long-term average annual atmosphere corrosivity parameters. The fact that metal corrosion depends on numerous climatic and aerochemical factors of the environment creates great difficulties for the quantitative estimation of the coefficients at the parameters used in DRFs. The coefficients for the main parameters can be obtained from the regularities found by statistical analysis of outdoor or laboratory tests. The use of the coefficients obtained for all dependences in DRFs does not ensure the prediction reliability
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