Machinery's Handbook, 31st Edition
Plating Standards 1645 reduce wear and prevent galling, corrosion, and seizure of metals. For use on aluminum, copper, steel, stainless steel, titanium, and chromium, and nickel bearing surfaces. Types I, II, and III have a thicknesses of 0.008 - 0.013 mm. No single reading less than 0.005 mm or greater than 0.018 mm. Type I has a curing temperature of 150 ± 15 ° C and an endurance life of 250 minutes; Type II, 204 ± 15 ° C and 450 minutes; and Type III is a low volatile organic compound (VOC) content lubricant with cure cycles of 150 ± 15 ° C for 2 hours, or 204 ± 15 ° C for 1 hour with an endurance life of 450 minutes. Color 1 has a natural product color and Color 2 has a black color. Nickel, QQ-N-290A: There is a nickel finish for almost any need. Nickel can be depos ited soft, hard-dull, or bright, depending on process used and conditions employed in plating. Thus, hardness can range from 150–500 HV (Vickers). Nickel can be similar to stainless steel in color, or can be a dull gray (almost white) color. Corrosion resistance is a function of thickness. Nickel has a low coefficient of thermal expansion. All steel parts having a tensile strength of 220,000 or greater shall not be a nickel plate without specific approval of procuring agency. Class 1 is used for corrosion protection. Plating shall be applied over an underplating of copper or yellow brass on zinc and zinc based alloys. In no case, shall the copper under plate be substituted for any part of the specified nickel thickness. Class 2 is used in engi neering applications. Grade A has a thickness of 0.0016 inch (41 μ m); Grade B, 0.0012 in. (30.48 μ m); Grade C, 0.001 in. (25.4 μ m); Grade D, 0.0008 in.(20.32 μ m); Grade E, 0.0006 in.(15.24 μ m); Grade F, 0.0004 in. (10.16 μ m); and Grade G, 0.002 in (50.8 μ m). Palladium, MIL-P-45209B: A gray, dense deposit good for undercoats. Has good wear characteristics, corrosion resistance, catalytic properties, and good conductivity. The thickness shall be 0.00005 in. (1.27 μ m) unless otherwise specified. Steel springs and other steel parts subject to flexure or repeated impact and of hardness greater than 40 RC are heated to 375 ± 25 ° F (190 ± 14 ° C) for 3 hours after plating. Chemical Passivation, ASTM A967: This process aims to improve the corrosion re- sistance of parts by removing contaminants from surfaces and facilitating formation of a passive oxide layer. Commercial passivation is performed on austenitic, ferritic, and martensitic stainless steels of the 200, 300, and 400 series, and related variants such as precipitation-hardening stainless steels. Passivation methods included in the standard are nitric acid immersion, citric acid im- mersion, and electrochemical treatment (See Electropolishing, ASTM B912-02 (2018) on page 1644). Nitric acid has long been used for chemical passivation, but safety and envi- ronmental concerns have led to the increasing use of citric acid, when possible. Various grades of stainless steel respond to passivation and related chemistry differently, so care must be taken when specifying a process. The efficacy of chemical passivation depends on the amount of dynamic contact be - tween the fluid and critical part surfaces. For parts with complex geometry, deep bores, or blind holes, the process may require agitation, repositioning, and use of fixtures. Phosphate Coating: Light, TT-C-490D: This specification covers cleaning methods and pretreatment processes. Methods / Types Typical Thickness (in.) Comments Cleaning Methods … Light coating for use as a paint base. Method I … Mechanical or abrasive cleaning (for ferrous surfaces only). Method II … Used for solvent cleaning. Method III … Used for hot alkalines (for ferrous surfaces only). Method IV … Emulsion. Method V … Used for alkaline derusting (for ferrous surfaces only). Method VI … Phosphoric acid.
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