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This specification covers the standard requirements for cadmium coatings vacuum deposited with or without supplementary chromate treatment on iron and steel basis metals. The cadmium metal for the production of the coating and the resultant coating shall conform to the chemical composition requirements as shall be determined by chemical, electrochemical, spectrochemical, or X-ray fluorescence analysis. Steel parts that have been machined, ground, cold-formed, or cold-straightened shall be heat treated for stress relief before cleaning and coating. The basis metal shall undergo surface cleaning, abrasive dry blasting, and outgassing by electron bombardment with high-energy positive ions to ensure satisfactory adhesion, abrasion resistance, and corrosion resistance performance. Chromate treatment shall be done in or with special aqueous acid solutions composed of hexavalent chromium along with certain anions that act as a catalyst or film forming compound to produce continuous, smooth, protective film. Coating adhesion shall be determined either by scraping or shearing with a sharp edge, knife, or razor blade through the coating down to the basis metal; plastically deforming by clamping and bending; or any suitable procedure such as burnishing, draw, or scribe tests. Salt spray corrosion test and visual examination shall also be performed on the coatings.
This abstract is a brief summary of the referenced standard. It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application. ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date.
Significance and Use
1.1 This specification covers the requirements for a cadmium coating vacuum-deposited on iron and steel basis metals. The coating is especially beneficial to those ferrous metals, heat treated to 46HRC and higher or having an ultimate tensile strength greater than 1500 MPa, wherein protection against corrosion and appearance are important (see Appendix X1).
1.2 Vacuum-deposited production items are normally free of hydrogen embrittlement, a danger when using electroplating processes for deposition. Vacuum deposition can handle large high-strength parts that cannot be conveniently mechanically plated in the rotating barrels.
1.3 The coating is provided in various thicknesses up to and including 12 μm (3.1) either in the as-deposited condition or with a supplementary finish (3.2).
1.4 The following precautionary caveat pertains only to the test methods portion, Section 9, of this specification: This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.
B117 Practice for Operating Salt Spray (Fog) Apparatus
B183 Practice for Preparation of Low-Carbon Steel for Electroplating
B201 Practice for Testing Chromate Coatings on Zinc and Cadmium Surfaces
B242 Guide for Preparation of High-Carbon Steel for Electroplating
B254 Practice for Preparation of and Electroplating on Stainless Steel
B320 Practice for Preparation of Iron Castings for Electroplating
B322 Guide for Cleaning Metals Prior to Electroplating
B440 Specification for Cadmium
B487 Test Method for Measurement of Metal and Oxide Coating Thickness by Microscopical Examination of Cross Section
B499 Test Method for Measurement of Coating Thicknesses by the Magnetic Method: Nonmagnetic Coatings on Magnetic Basis Metals
B504 Test Method for Measurement of Thickness of Metallic Coatings by the Coulometric Method
B567 Test Method for Measurement of Coating Thickness by the Beta Backscatter Method
B568 Test Method for Measurement of Coating Thickness by X-Ray Spectrometry
B571 Practice for Qualitative Adhesion Testing of Metallic Coatings
B602 Test Method for Attribute Sampling of Metallic and Inorganic Coatings
B697 Guide for Selection of Sampling Plans for Inspection of Electrodeposited Metallic and Inorganic Coatings
E396 Test Methods for Chemical Analysis of Cadmium
F519 Test Method for Mechanical Hydrogen Embrittlement Evaluation of Plating/Coating Processes and Service Environments
ICS Number Code 25.220.40 (Metallic coatings)