Temperature influenced corrosion

The effect of temperature on corrosion rate is influenced by the following factors [188] ... 

Ruther, W. E. and Hart, R. K., Influence of Oxygen on High Temperature Aqueous Corrosion of Iron , Corrosion, 19, 127t (1963)... 

Active microbiologically influenced corrosion (MIC) of metal due to bacteria is quite complex. It can involve several species of microorganisms and is affected by temperature, TOC, pH, and other factors. Examples of bacterial species which are associated with MIC are described below ... 

The behavior of RubCon at elevated and negative temperatures in nonaggressive environmental operating conditions have been studied [24], Continuation of this research involves the examination of RubCon resistance in liquid corrosive environments at elevated temperatures, which showed visual destruction of the material. The combined influence of temperature and corrosive medium was determined by testing RubCon specimens measuring 4 x 4 x 16 cm. Experiments were performed in a 10% solution of caustic soda and a 30% solution of sulfuric acid at temperatures of 40°C and 60°C. Results of the experiments are illustrated in Table 2.8. 

FM5. Corrosion. The positive grid is subject to corrosion. The rate of this debilitating process is influenced by grid composition and microstructure, plate potential, electrolyte composition, temperature. The corrosion product is generally more electrically resistive than the grid and thus diminishes the output of the battery. In extreme cases, corrosion results in disintegration of the grid and collapse of the plate. 

Ethyl silicate binders are mainly used in applications involving high temperatures and corrosive influences. The principal application of ethyl silicate zinc dust coatings is the protection of iron and steel against corrosion it is effective even at temperatures of up to 400 C. Examples include ships, harbor construction work, bridges, steel structures exposed to atmospheres in industrial areas, tanks, containers, pipelines, and chimneys. 

FIGURE 4.55 What corrosion rates incases of MIC may look like. Bacteria are active within a temperature range, below and above which their activity and thus their contribution to corrosion decrease. (With kind permission from Springer Science+Business Media Microbiologically Influenced Corrosion—An Engineering Insight, 2008, Javaherdashti R.)... 

In addition to temperature, pitting corrosion is influenced by two factors ... 

Expxrsure tempjerature— In general, corrosion rates increases with temperature. However, corrosion rate/temprerature relationships can be strongly influenced by system geometry and impurity effects. 

Temperature - maximum Peak temperature attained my influence corrosivity... 

At low concentration, the temperature influence is more marked. It strongly decreases as the concentration increases, reaching a maximum level. It joins the previously suggested idea of a phenomenon of saturation of the corrosive diffusion. This saturation could explain the observed limitation of the diffusion speed. This limitation also depends on the gradual creation of decomposition products of chemical species during the mechanism of destruction of tissue by the corrosive agent. 

In general, temperature is a factor influencing corrosion rates, but it is of little importance except under extreme conditions. 

On the basis of these results it could be demonstrated that a medium containing even small amounts of fluoride (10 to 50 mg L ) and a normal chloride content increases the susceptibility to localized corrosion. In general, increasing chloride and fluoride content, increasing temperature, and decreasing pH are factors influencing corrosion susceptibility. 

Another important parameter is the dependence of the float current on float voltage and the temperature. Both parameters markedly influence the float current and thereby the water loss by electrolysis. Furthermore, both parameters also influence corrosion of the grid and all conducting elements that are connected to the positive plate. 

Castings are produced by different molding processes green sand, air-set sand, resin-bonded sand, rammed graphite, investment, etc. The corrosion resistance of an as-cast surface is a function of the moulding process, pouring temperature, and mold surface treatments or mold washes. Carbon pick-up and mold reactions are just two of the factors that influence corrosion resistance. The corrosion resistance of most machined surfaces will be independent of the molding process provided that 1/16-1/8 in. of material is removed. 

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