ASTM-B733:2015 pdf free download – Standard Specification for Autocatalytic (Electroless) Nickel-Phosphorus Coatings on Metal.
7.2.3 Adhesion—The coating shall have sufficient adhesion to the basis metal to pass the specified adhesion test (see 9.4 and Practice B571).
7.2.4 Porosity—The coatings shall he essentially pore free when tested according to one of the methods of 9.6. The test method, the duration of the test, and number of allowable spots per unit area shall he specified (see 5.1.11 and 9.6).
7.3 Qualification Requireinen ts—These requirements are placed on the deposit and process and are performed on specimens to qualify the deposit and plating process. The tests for these qualification requirements shall he performed monthly or more frequently.
7.3.1 Composition—Type II, III, IV, V deposits shall be analyzed for alloy composition by testing for phosphorus (see 9.1). The weight percent of phosphorus shall be in the range designated by type classification (see 4.1).
7.3.2 Microhardness—The microhardness of Class 2 deposits shall be determined by Test Method B578 (Knoop). For Class 2 coatings, the microhardness shall equal or exceed a minimum of 850 (HK100 (or equivalent Vickers) (see 4.3 and 9.5). The conversion of Vickers to Knoop using Tables E140 is not recommended.
7.3.3 Hydrogen Emhri1e,nent—The process used to deposit a coating onto high strength steels shall be evaluated for hydrogen embrittlement by Test Method F5 19.
8. Sampling
8.1 The purchaser and producer are urged to employ statistical process control in the coating process. Properly performed this will ensure coated products of satisfactory quality and will reduce the amount of acceptance inspection.
8.1.1 Sampling plans can only screen out unsatisfactory products without assurance that none of them will he accepted.
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8.2 The sampling plan used for the inspection of a quantity of coated parts (lot) shall be Test Method B602 unless otherwise specified by purchaser in the purchase order or contract (see 5. 1. 12 and S. 11 . 1).
NOTE lO—Usually. when a collection of coated parts (the inspection lot 8.2) is examined for compliance with the requirements placed on the parts a relatively small number of parts, the sample, is selected at random and inspected. The inspection lot is then classified as complying or not complying with the requirements based on the resuhs of the inspection sample. The size of the sample and the criteria of compliance are detemiined by the application of statistics. The procedure is known as sampling inspection. Three standards Test Method B602, Guide B697, and Test Method B762 contain sampling plans that are designed for the sampling inspection of coatings.
Test Method B602 contains four sampling plans, three for use with tests that are nondestructive and one for use with tests that are destructive. The purchaser and producer may agree on the plan(s) to be used. If they do riot, Test Method B602 identifies the plan to be used.
Guide B697 provides a large number of plans and also gives guidance on the selection of a plan. When Guide B697 is specified, the purchaser and producer need to agree on the plan to be used.
Test Method B762 can be used only for coating requirements that have a numerical limit, such as coating thickness. The last must yield a numerical value and certain statistical requirements must be met. Test Method B762 contains several plans and also gives instructions for calculating plans to meet special needs.