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Mechanical Engineers Data Handbook Episode 11

Tham khảo tài liệu 'mechanical engineers data handbook episode 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 240 MECHANICAL engineer s data handbook Properties of pure metals Metal m.p. C p kgm 3 E GNnT2 G GNm 2 RSHC a xio6 c- Po lơtíì-m ar mfiT-1 ECE mg c-1 Aluminium 659 2700 70 27 0.21 23 245 450 0.093 Copper 1083 8900 96 38 0.09 17 156 430 0.329 Gold 1063 19 300 79 27 0.03 14 204 400 0.681 Iron 1475 7 850 200 82 0.11 12 890 650 0.193 Lead 327 11 370 16 0.03 29 1900 420 1.074 Mercury 13 580 0.03 60 9410 100 1.039 Nickel 1452 8 800 198 0.11 13 614 680 0.304 Platinum 1775 21040 164 51 0.03 9 981 390 0.506 Silver 961 10 530 78 29 0.06 19 151 410 1.118 Tungsten 3400 19 300 410 0.03 4.5 490 480 0.318 Zinc 419 6860 86 38 0.09 30 550 420 0.339 m.p. melting point p density E Young s modulus G shear modulus RSHC relative specific heat capacity a coefficient of linear expansion p resistivity at o c Ct resistance temperature coefficient at o c ECE electrochemical equivalent. 6.12 Corrosion of metals 6.12.1 Corrosion prevention Corrosion may be prevented by considering the following points. Material selection Metals and alloys which resist corrosion in a particular environment can be used. Proximity of metals with large potential difference e.g. a copper pipe on a steel tank should be avoided. Galvanic protection can be used e.g. by use of a sacrificial anode of zinc close to buried steel pipe or a ship s hull. Appropriate design Crevices which hold water e.g. bad joints and incomplete welds should be avoided as should high tensile stresses in material subject to stress corrosion. Locked-in internal stress due to forming should be avoided. Modified environment Metals can be enclosured against a corrosive atmosphere water etc. Drying agents e.g. silica gel and corrosion inhibitors e.g. in central-heating radiators can be used. Protective coating Metals can be coated to make them impervious to the atmosphere water etc. by use of a coating of grease plasticizer bitumen resins polymers rubber latex corrosion-resistant paints or metal coating. 6.12.2 Corrosion resistance of metals .