Volume 05 - Surface Engineering Part 13 pps

Illustration of the mechanism of corrosion for painted steel (a) and painted galvanized steel (b) (a) A void in the paint results in rusting of the steel, which undercuts the paint coating and results in further coating degradation (b) A void in the coating of a painted galvanized steel is sealed with zinc corrosion products; this avoids the undercutting seen in (a) and prevents further deterioration of the painted coating Table 20 Synergistic protective effect of galvanized steel/paint systems in atmospheric exposure Type of Atmosphere Galvanized steel Paint Thickness Thickness μm mils Service life(a), years μm Galvanized plus paint mils Service life(a), years Thickness μm mils Service life(a), years Paint adhesion Hot Dip Aluminum Coatings Microstructure of type aluminum coating on steel This coating forms a layer of essentially pure aluminum (top) with scattered gray particles of aluminum-iron; the light gray center layer is aluminum-iron, and the bottom layer is the base steel 1000× Microstructure of type aluminum coating on steel From top: a nickel filler, aluminum-silicon alloy, aluminum-silicon-iron alloy, and steel base metal 1000× Table 21 Coating thickness losses for galvanized steel and type aluminized steel in atmospheric exposure Years exposed Middletown, OH Kure Beach, NC G90(a) Type G90 μm μm μm mils mils Type mils μm mils Corrosion Mechanism Corrosion in Natural Waters O O Corrosion in Seawater μ μ Table 22 Applications of diffused aluminum hot dip coatings for resistance to oxidation and corrosion at 455 to 980 °C (850 to 1800 °F) Product and base metal Heat treating equipment Heat exchanger components Fasteners Type of service Miscellaneous equipment Effects of coating thickness and exposure temperature on oxidation of coated and uncoated steel Oxidation at 480 to 870 °C (900 to 1600 °F) Steel 6.4 mm ( 870 °C (1600 °F) in.) thick was completely oxidized after 700 h at Materials, Finishing and Coating, Tool and Manufacturing Engineers Handbook, Materials, Finishing and Coating, Tool and Manufacturing Engineers Handbook, Protective Coatings for Metals, Metal Corrosion in the Atmosphere, Zinc: Its Corrosion Resistance, Metallwissenschaft Technik, Thermisch Verzinken, ASM Specialty Handbook: Aluminum and Aluminum Alloys, Materials, Finishing and Coating, Tool and Manufacturing Engineers Handbook, Iron Steel Int., J Mater Sci., Encyclopedia of Materials Science and Engineering, Atmospheric Corrosion Investigation of Aluminum-Coated, Zinc-Coated, and Copper Bearing Steel Wire and Wire Products (A 12 Year Report), The Corrosion of Light Metals, Atmospheric Corrosion, Transportation Research Record 1001, Microstructure of an aluminum-zinc coated sheet Ω 23 Effect of laser scribing on the core loss of a high-permeability grain-oriented electrical steel Source: Ref Purpose Materials, ASM Handbook Properties and Selection: Nonferrous Alloys and SpecialMetals Handbook Materials Transactions, J/M, Proc Conf ICALEO 1984, p 102-111 core loss Revised by F.S Pettit, University of Pittsburgh ASM Handbook Table Procedure for removing scale from heat-resistant alloys Operation Time, Temperature °C Solution Concentration °F Precleaning cycle Scale-conditioning cycle Pickling cycle Table Procedure for removing scale from Inconel alloys Operation Time Temperature °C °F Solution(a) Concentration(a) Table Procedure for sodium hydride descaling and acid pickling of heat-resistant alloys Operation Time Temperature °C °F Solution(a) Concentration, vol %(a) Table Procedure for stripping copper plate Table Procedure for stripping nickel plate Metals Handbook, Metals Handbook, Metals Handbook, Table Conditions for abrasive blast cleaning of aluminum products with silica Grit size Mesh Nozzle diameter Nozzle to work(a) Air pressure mm mm kPa in in psi Table Applications for abrasive blast cleaning of aluminum products Product Size mm Pieces, h Abrasive in Type Mesh size Blasting to prepare for organic coating Blasting for appearance produced Table Conditions for wet blasting of aluminum-base materials Operation Abrasive Type Mesh size Copyright â 2002 ASM Internationalđ All Rights Reserved Table Conditions for wet barrel finishing of aluminum products Product No of pieces per kg lb Clean, deburr and brighten(a) Deburr and brighten(b) Burnish to high gloss(c) No of pieces per load Cycle time, Barrel speed, rev/min ... build-up alloys and metal-to-metal wear alloys Alloy Composition, wt% Hardness, HRC Abrasion, volume loss Low-stress(c) Fe Cr C Build-up weld overlay Metal-to-metal weld overlay Si Mn Mo Ni High-stress(d)... 34 Service-life estimates for aluminum and 90Al-10MMC (vol%) thermal spray coatings Type of exposure Coating thickness required for indicated service life(a) 5-1 0 years 1 0-2 0 years 2 0-4 0 years... 30 Melted-oxide compositions of frits for ground coat enamels for sheet steel Constituent Composition, % Regular blue-black enamel Alkali-resistant enamel Acid-resistant enamel Water-resistant