Wear and Corrosion

Alloy Breakdown Potential (mV) V5. Standard Calomel Electrode Repassivation Time (ms) -500 mV +500 mV  

Alloy Corrosion Potential Ecorr (mV) Passive Current Density Ip ([xA/cm ) Breakdown Potential (mV) 

Alloy 1000 cycles Weight loss ( xg) after 3000 cycles 5000 cycles 

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). 

The combined action of wear or abrasion and corrosion results in more severe damage than with either mechanical or corrosive attack alone. The metal removed from the surface can be metal ions, or as particles of solid corrosion products or as elemental metal. The erosion-corrosion process ranges from primarily erosive attack such as sandblasting, filing, or grinding of metal surface to essentially corrosion failures devoid of mechanical action. 

Corrosion can occur in the absence of mechanical wear, but the opposite is rarely true. Corrosion often occurs in a wear process to a certain extent in all environments. 

ASTM F746-81 test (mV) Scratch test (mV) Potentiodynamic test Current 10 p,A/cm (mV) Repassivation (mV) 

Critical pitting temperature test Potentiostatic 200 mV (°C) Potentiostatic 350 mV (°C) Critical crevice temperature test Potentiostatic 200 mV (°C) Potentiostatic 350 mV (°C) 

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K. N. Strafford, P. K. Datta, and G. G. Googan, eds.. Coatings and Suface Treatment for Corrosion and Wear Resistance, Halstead Press, New York,... 

Steam treatment imparts increased corrosion resistance for ferrous P/M parts. The parts are heated to 400—600°C and then exposed to superheated steam. After cooling, the parts are usually oil dipped to further increase corrosion and wear resistance, and to enhance appearance (see Corrosion and CORROSION control). Heat treated parts are seldom steam treated because annealing reduces hardness and tensile strength. 

Chromium carbide is important in powder preparations designed for thermal spray apphcations of corrosion and wear-resistant coatings on tool and machine parts. Lower carbon carbides of chromium are important in hardfacing tods and electrodes for weld-apphed ovedays on machine wear surfaces. However, these carbides are usually formed in situ from Cr and C in the rod and not added as preformed carbides. The properties of Ci2C2 are hsted in Table 2. 

The most important nitride of Si is Si3N4 this is formed by direct reaction of the elements above 1300 or more economically by heating Si02 and coke in a stream of N2/H2 at 1500". The compound is of considerable interest as an engineering material since it is almost completely inert chemically, and retains its strength, shape and resistance to corrosion and wear even above 1000°. ° Its great hardness (Mohs 9), high... 

Excessive particulate contamination of the fluid indicates that the filters are not keeping the system clean. This can result from improper filter maintenance, inadequate filters, or excessive ongoing corrosion and wear. 

Jones, R. D. and Jones, D. P., Hot-dip Aluminized Steel Strip for Corrosion Resistant Applications , in Surface Treatment for Corrosion and Wear Resistance, Strafford, Datta and Googen (eds), Ellis Horwood, Chichester (1984)... 

Harris, S. J., Green, P. D. and Cobb, R. C., Thermally Sprayed Al-Zn-In-Sn Alloys in 3rd Int. Conf. on Advances in Surface Engineering for Corrosion and Wear Resistance, Newcastle-upon-Tyne, 1-10(1992)... 

The recovery of petroleum from sandstone and the release of kerogen from oil shale and tar sands both depend strongly on the microstmcture and surface properties of these porous media. The interfacial properties of complex liquid agents—mixtures of polymers and surfactants—are critical to viscosity control in tertiary oil recovery and to the comminution of minerals and coal. The corrosion and wear of mechanical parts are influenced by the composition and stmcture of metal surfaces, as well as by the interaction of lubricants with these surfaces. Microstmcture and surface properties are vitally important to both the performance of electrodes in electrochemical processes and the effectiveness of catalysts. Advances in synthetic chemistry are opening the door to the design of zeolites and layered compounds with tightly specified properties to provide the desired catalytic activity and separation selectivity. 

D. J. Mills. In Coatings and Surface Treatment for Corrosion and Wear Resistance Strafford, K. N., Ed. Norwood Chichester, England, 1984 pp. 315-30. 

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. 

Cylinder and piston ring wear have been observed when using alcohol fuels. Metal loss could be due to wear caused by removal of the lubricating oil film by liquid alcohol during cold starting or by the corrosive action of formic acid or other acids formed during the combustion process. Use of more corrosion- and wear-resistant metal alloys in engine construction have helped resolve this problem. 

Electroplating of one metal onto another is widely used for protection against corrosion and wear or for cosmetic purposes.16 Again, the source of metal for deposition could be anodic dissolution or a prepared solution with an inert anode. In contrast to electrolytic refining, only a very thin layer (typically on the order of 1 to 10 pm) of the plating metal is wanted, but usually this layer must be uniform, cohesive, and nonporous, and often a shiny appearance is desired. To understand the roles of some of the variables in electroplating, it is useful to consider the electrodeposition... 

Chromizing and Related Diffusion Processes. Chromizing is similar to aluminizing. A thin corrosion and wear resistant coaling is applied to low cost steels such as mild steel, or to a nickel-based alloy. In the related boroni/ing process, a thin boron alloy is produced for extreme hardness, wear, and corrosion resistance. Siliconizing is yet another process used especially lor coaling of the refractory metals Ti. Nb. Ta. Cr. Mo. and W. 

Reduce junking frequency. Design for corrosion and wear resistance easy maintainability. Discourage frequent styling changes simply in interest of increasing marketing appeal. 

V.S. Sastri, M. Elboudjaini and J.R. Perumareddi, Economics of Corrosion and Wear in Aerospace Industry, Proc. of the International Conference on Aerospace Materials, Metallurgical Society of CIM, Montreal, 12-15 August 2002. 

The most important step in failure analysis is to identify the damage mechanism involved in the failure. In the broad sense damage mechanisms are classified as distortion, fracture, corrosion and wear. That this classification is simplistic is... 

Table 4.55 Nominal composition of aqueous corrosion and wear-resistant cobalt alloys...

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... 

Testing. The measurement of corrosion, wear, and corrosion-wear interactions as well as erosion-corrosion interactions is a multistep process. Each component of the interaction must be measured separately. The results may then be combined to identify the synergistic effects and create a complete picture of the damage process. Measurement of the interaction between corrosion and wear modes or damage is more difficult. The standard (ASTM, G119)4 applies to systems in liquid solutions or slurries and some aspects of it can be adapted to dry corrosion and wear interactions as well. (Tylczak and Adler)5... 

Weld Metal Overlay a Cost-effective Solution to High-temperature Corrosion and Wear Problems... 

High-temperature corrosion and wear is encountered in various industries such as waste incineration, fossil energy, pulp and paper, petroleum refining, chemical and petrochemical, mining and smelting operations. One of the methods to combat corrosion and wear and its control is to select suitable material, i.e., an alloy, for the plant design and maintenance. The selection of proper material for plant design and fabrication is followed... 

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. 

Chromium Increases the hardness of the steel and improves its wear or abrasion resistance. It helps to limit grain size. If added in amounts greater than 5%, it can impart corrosion and wear resistances. 

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