Corrosive Wear of Metals

Mechanochemical wear is an intricate process in which corrosive damage and mechanical wear are interrelated [1,2]. The role of corrosive and mechanical factors in corrosion-induced wear of metals in electrodes is estimated in different ways. Some authors consider this process as purely corrosive, others 

Proceeding from the above, corrosive wear is conditioned by a group of effects of different nature. It is actually impossible to differentiate between these effects or to analyze their influence on friction and wear separately as they are in fact inseparable what is more, it is incorrect to speak about additivity of their interactions. 

Among the factors governing corrosive wear, it is justifiable to mention the following [1]  

This classification has perhaps gone too far in its usage of complex terms but it vividly visualizes the multitude of chemical phenomena emerging under conditions of contact friction. Besides, the subdivision of tribochemistry into branches should not be understood as to indicate the nonexistence of individual chemical mechanisms in one particular contact. The chemical. 

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Combustion products can cause corrosive wear of metal. 

Marine fuel sulfur can range from 1.5 wt% for DMA to as high as 5.0% for RME and higher-viscosity grades of marine residual fuel. Problems related to sulfur include high SOx emissions and the formation of sulfuric and other acids within the fuel combustion system. At low temperatures, the formation and condensation of acids within the combustion chamber can result in corrosion and wear of metal system components. 

Corrosion and Wear. The progressive deterioration, due to corrosion and wear, of metallic surfaces in use in major industrial plants ultimately leads to loss of plant efficiency and in the worst case to shutdown. For example, corrosion and wear damage to materials, both directly and indirectly, cost the United States economy almost 300 billion per year at current prices. Similar studies on wear failure have shown that the wear of materials costs the U.S. economy about 20 billion per year... 

G. Lai, M. Jirinec, P. Hulsizer and F. Novae, Proceedings of International Symposium on Corrosion and wear of Metals Metallurgical Society of Canadian Institute of Mining, 36th Annual Conference, Sudbury, Ontario, Canada, August 1997. 

The overall national costs of corrosion of metal and fracture of all materials are each about of the GNP, 20-30% of which could be saved with complete use of economic best practice. The costs of wear, which are not as well known, raise the total costs of these three degradative processes to somewhat over 10% of the GNP. The costs are expected to be comparable in other industrialized nations. From the results in Ref. 18, the extra corrosion costs of metals associated with air pollution are about 0.15% of the GNP, or H% of the total corrosion costs. 

Chemical and oxidative effects during friction and wear of metals have been studied at length in atmospheric conditions, corrosive liquid media and high temperatures. Nevertheless, it is hard to establish any common patterns in these wear factors. Let us take some examples. 

Mechanochemical wear is a complex process during which electrochemical solution of metals catalyzes fatigue failure. Friction, in turn, activates electrochemical corrosion. As can be seen, the process of mechanochemical wear of metals in electrolytes has a combined fatigue-electrochemical nature. 

The efficiency of polymer materials as an anticorrosion mean of protection of metal parts from corrosion can be significantly raised by modification of polymer binders using corrosion inhibitors for metals. In this case it becomes possible to realize both the barrier and inhibition mechanisms for metal protection from corrosion in the anticorrosion element. Anticorrosion polymer elements as a source of electric field can hamper corrosion processes and corrosion-mechanical wear of metal parts by the electrochemical mechanism. Realization of the barrier, inhibition and electrochemical mechanisms of anticorrosion protection with the help of polymers not only allows a profound improvement in the anticorrosion protection of metal parts but comes close to the creation of smart anticorrosion plastics and anticorrosion systems. 

The progressive deterioration, because of corrosion and wear, of metallic surfaces leads to loss of plant efficiency, and in the worst case, to shutdown. For instance, both direct and indirect costs to the US economy have been estimated to be nearly 300 billion per year. The wear of materials has been estimated to cost 20 billion a year (in 1978 dollars) compared to 80 billion for corrosion during the same period (9, 58). 

R.L. Pozzo and I. Iwasaki, Effect of Pyrite and Pyrrhotite on the Corrosive Wear of Grinding Media, Miner. Metall. Process., Aug 1987, p 166-171... 

These units are made of abrasion resistant metals, solid plastics, or tvith corrosion/wear resistant plastic liners. 

Another major cause of wear is the chemical action associated with the inevitable acidic products of fuel combustion. This chemical wear of cylinder bores can be prevented by having an oil film which is strongly adherent to the metal surfaces involved, and which will rapidly heal when a tiny mpture occurs. This is achieved by the use of a chemical additive known as a corrosion inhibitor. 

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