ASTM B893-98(R2018) pdf free download

ASTM B893-98(R2018) pdf free download.Standard Specification for Hard-Coat Anodizing of Magnesium for Engineering Applications
1. Scope
1.1 This specification covers requirements for electrolyti- cally formed oxide coatings on magnesium and magnesium alloy parts where appearance, abrasion resistance, and protec- tion against corrosion are important. 1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.3 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
5. Ordering Information (to be supplied by the purchaser to the producer.) 5.1 Alloy Designation—When ordering articles anodized in accordance with this specification, the purchaser shall state, the alloy designation number. 5.2 Appearance—Unless otherwise specified by the purchaser, an off-white color shall be acceptable for TYPE A coating. The purchaser shall specify the color and surface appearance required for TYPE B coatings. All coatings shall be uniform in color and free from stains. Alternatively, samples showing the required finish, or range of finishes, shall be supplied or approved by the purchaser. When required, the basis material may be subjected to such mechanical polishing as may be required to yield the desired final surface character- istics.5.3 Significant Surface—The areas of the article covered by the coating, for which the coating is essential for service or appearance or both. 5.3.1 Contact Marks—Contact marks will occur. The pur- chaser shall specify where contact marks are unacceptable. 5.4 Tolerances—Dimensional build-up is approximately one-half of anodic film thickness. The order document shall include any coating thickness tolerances and shall not exceed any applicable drawing dimensions. 5.5 The purchaser shall provide the number for this standard TYPE. 5.6 The purchaser shall state any special post treatments (see 4.2 and 5.2). 5.7 Test Methods—The purchaser shall state the test meth- od(s) by which the coated article will be evaluated (see Section 8). 5.8 Sampling Plan—see Section 9. 5.9 Any requirement for certification (see Section 11). 5.10 Any requirement for packaging (see Section 12).
6. Materials and Process
6.1 Process: 6.1.1 Basis Metal—This specification does not specify re- quirements for the surface condition of the basis metal before anodizing, but agreement should preferably be reached be- tween the purchaser and the producer that the surface condition of the basis metal is satisfactory. 6.1.2 Surface Preparation—Preparatory procedures and cleaning of the basis material may be necessary, see Practice B322. 6.1.3 Hard-Coating—Following the preparatory operations, the articles are introduced into the solution for a period of time at the current density and temperature required to produce the hard-coated surface. N OTE 1—Hard-coating solutions and operating conditions are commer- cially available. The appropriate operating instructions should be fol- lowed. N OTE 2—Intricately shaped articles may not receive the same thickness of coating in recessed areas due to lower current densities. Auxiliary cathodes, may be used to improve anodize thickness in these areas. 6.2 Post Treatments: 6.2.1 Final Rinsing—Rinsing subsequent to anodizing is necessary to remove all traces of the electrolyte that may affect the appearance and performance of the part. Deionized or distilled water may be used to avoid water spots. 6.2.2 Post Treatment—Surface sealers or topcoats may be specified to reduce friction, add color, or further increase performance.