ASTM B840-15 pdf download.Standard Specification for Electrodeposited Coatings of Zinc Cobalt Alloy Deposits.
7. Sampling 7.1 The sampling plan used for the inspection of a quantity of the coated articles shall be as agreed upon between the purchaser and the seller. N OTE 7—Usually when a collection ofcoated articles, the inspection lot (7.2), is examined for compliance with the requirements placed on the articles, a relatively small number ofthe articles, the sample, is selected at random and is inspected. The inspection lot is then classified as complying or not complying with the requirements based on the results of the inspection of the sample. The size of the sample and the criteria of compliance are determined 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 nondestruc- tive and one when they are destructive. The buyer and seller may agree on the plan or plans to be used. If they do not, Test Method B602 identifies the plan to be used. Guide B697 provides a large number ofplans and also gives guidance in the selection of a plan. When Guide B697 is specified, the buyer and seller 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 a coating thickness. The test 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. The buyer and the seller may agree on the plan or plans to be used. If they do not, Test Method B762 identifies the plan to be used. N OTE 8—When both destructive and nondestructive tests exist for the measurement of a characteristic, the purchaser needs to state which is to be used so that the proper sampling plan is selected. Atest may destroy the coating but in a noncritical area; or, although it may destroy the coating, a tested part can be reclaimed by stripping and recoating. The purchaser needs to state whether the test is to be considered destructive or nondestructive. 7.2 An inspection lot shall be defined as a collection of coated articles that are ofthe same kind, have been produced to the same specification, have been coated by a single supplier at one time or at approximately the same time under essentially identical conditions, and are submitted for acceptance or rejection as a group.
7.3 Ifspecial test specimens are used to represent the coated articles in a test, the number used shall be that required in 8.1.1.
8. Test Methods
8.1 Special Test Specimens:
8.1.1 The permission or the requirement to use special test specimens, the number to be used, the material from which they are to be made, and their shape and size shall be stated by the purchaser.
N OTE 9—Test specimens often are used to represent the coated articles in a test if the articles are of a size, shape, or material that is not suitable for the test or if it is preferred not to submit articles to a destructive test because, for example, the articles are expensive or few in number. The specimen should duplicate the characteristics of the article that influences the property being tested.
8.1.2 Special test specimens used to represent articles in an adhesion, porosity, corrosion resistance, or appearance test shall be made of the same material, shall be in the same metallurgical condition, and shall have the same surface condition as the articles they represent. They shall be placed in the production lot of and be processed along with the articles they represent. 8.1.3 Special test specimens used to represent articles in a coating thickness test may be made ofa material that is suitable for the test method even if the represented article is not of the same material. For example, a low-carbon steel specimen may represent a brass article when the magnetic thickness test is used (Test Method B499). The thickness specimen need not be carried through the complete process with the represented article. Ifnot, it shall be introduced into the process at the point where the coating is applied and it shall be carried through all steps that have a bearing on the coating thickness. In rack plating, the specimen shall be racked in the same way with the same distance from and orientation with the anodes and other items in the process as the article it represents. N OTE 10—When special test specimens are used to represent coated articles in a thickness test, the specimens will not necessarily have the same thickness and thickness distribution as the articles unless the specimens and the articles are of the same general size and shape. Therefore, before finished articles can be accepted on the basis of a thickness test performed on special test specimens, the relationship between the thickness on the specimen and the thickness on the part needs to be established. The criterion of acceptance is that thickness on the specimen corresponds to the required thickness on the article. 8.2 Composition ofCoating—The composition of the coat- ing shall be verified by atomic absorption spectrophotometry (AA), inductively coupled plasma (ICP), or directly coupled plasma (DCP) or other methods if found to be capable of results within 10 % of known standards. 8.3 Appearance—The coating shall be examined at up to 10× magnification for conformance to the requirements of appearance. 8.4 Thickness—The coating thickness shall be measured at locations on the significant surface designated by the pur- chaser, and the measurement shall be made with an accuracy of 10 % or better by use of one of the following standards, Test Methods B487, B499, B504, and B568. 8.5 Adhesion—The adhesion ofthe coating shall be tested in accordance with Practice B571. The choice oftest method shall be one of those appropriate for zinc coatings. 8.6 Corrosion Resistance—See Appendix X1.ASTM B840 pdf download.