1.1 本指南提供了用于检查产品上金属和无机涂层的抽样计划，以确定提交的大量涂层产品是否符合适用于涂层的规范。 1.2 抽样计划是变量计划。在这种类型的计划中，从一个生产批次中提取几件产品。测量了拉制物品上涂层的特性。获得的值用于估计批次中不符合数字限制（例如最小厚度）的物品数量。将该数字与允许的最大值进行比较。 1.3 只有当感兴趣的特性是可测量的，测试方法给出了特性的数值测量，并且规范对测量值设定了数值限制时，才能使用变量计划。生产批次中不同产品的特性变化也必须是正态分布的（参见 附录X2 ). 每个物品必须以相同的方式进行测试（例如，必须在同一位置测量涂层厚度，请参阅 X2.7 )因此，各条款的价值具有可比性。如果不满足其中一个或多个条件，则无法使用变量计划。相反，必须使用属性计划。这些在指南中给出 B602 和指南 B697 . 1.4 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.5 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 抽样检查允许通过检查从一组产品中抽取的数量相对较少的产品来估计一组产品的整体质量。 5.2 抽样计划的规范为买方和卖方提供了一种确定被认为满意的最低质量水平的方法。 5.3 由于抽样计划产生了对产品质量的估计，因此检验结果会有误差。通过选择抽样方案，了解并控制潜在误差。 5.4 当必须决定如何处理大量物品时，使用抽样检查。该数量可以是供应商发货、准备后续制造操作的物品或准备发货给客户的物品。 5.5 在抽样检查中，从大量物品（检验批）中随机选择数量相对较少的物品（样品）； 检查样品是否符合物品上的要求。根据结果，决定批次是否符合要求。 5.6 由于只对生产批次的一部分进行了检查，因此未检查物品的质量未知。存在一些未经检查的物品不合格的可能性。因此，任何抽样检查计划的基础是买方是否愿意接受包含一些不合格品的批次。验收批次中不合格品的数量由样本的大小和放置在样本上的验收标准控制。 5.7 验收抽样计划用于以下原因: 5.7.1 当检验成本高且验收不合格品的后果不严重时。 5.7.2 当100 % 检查是疲劳和无聊的，因此，可能会导致错误。 5.7.3 当检验需要进行破坏性试验时，必须进行抽样检验。 5.8 在通过变量进行验收抽样时，测量样品中每个物品的涂层特性。使用这些值的算术平均值、过程的标准偏差和因子 k 如表中所示，计算出一个数字（参见 9.3 ). 如果该数量等于或超过规定的最小值，则检验批符合要求。如果数量较少，则该批次不符合要求。如果过程的标准偏差未知，则计算并使用样品的标准偏差。 5.9 抽样计划的使用涉及到检验成本与接受数量不合要求的不合格品的后果之间的平衡。总是存在这样的风险:随机样本无法正确描述抽取批次的特征，并且不可接受的批次将被接受或可接受的批次将被拒绝。 样本越大，风险越小，但检查成本越高。 5.10 为了了解风险，考虑如果检验批中的每一件物品都符合其要求，那么样品中的每一件物品也将符合其要求。此类标段将被接受( 注1 ). 如果一个检验批中只有少数物品不合格，样品可能会表明该批物品是可接受的；但样本表明该批次不可接受的可能性很小。检验批中不合格品的比例越大，样品表明该批不合格的可能性越大。如果检验批中的每件物品都不合格，则样品将始终表明该批物品不合格。 注1: 在整个方法中，假设在采样、测量和计算中没有错误。 5.11 验收包含不合格项目的检验批的概率通常用可接受质量水平（AQL）和极限质量水平（LQL）来描述。 AQL是被认为可以接受的质量水平。LQL是一种被认为几乎无法容忍的质量水平。选择一个抽样方案，该方案具有接受大量AQL质量和拒绝大量LQL质量的高概率。在该方法中，为抽样计划给出的AQL是具有95 % 被接受的可能性。LQL是具有10的批次的质量水平 % 被接受的概率，换句话说，90 % 被拒绝的概率。该方法中的表格给出了每个计划的AQL和LQL。他们还给出了50/50分，即一批产品的质量水平，即被接受和被拒绝的可能性相同。 5.12 不合格检验批的处置不在本方法的范围内，因为根据情况，可能会将批次退回给供应商、保留和使用、用于其他用途、报废、返工或以其他方式处理。 另一种选择是校正检查，其中筛选并使用拒收批次。 5.13 在矫正检查中，当一个检验批被拒绝时，该批中的所有物品都将被检查，不合格的物品将被移除。可以用合格品替换。now 100 % 合格批次被接受。通过这种做法，由于增加了100个批次，整体上一系列批次的平均质量水平将更好 % 合格批次。当进入的批次质量水平良好时，当筛选并重新提交被拒绝的批次时，一系列批次的平均质量水平将更好。当进货批次的质量水平较差时，一系列接受批次的平均质量将再次良好，因为许多进货批次将被拒绝并升级。在进货批次的中等质量水平下，一系列验收批次的平均质量水平将再次得到改善，但不会像上述任何一种情况那样得到改善； 并且将有一个中等质量水平，其中改进程度最低。这种改进的质量级别称为平均输出质量限制（AOQL）。这是矫正检查时可能出现的最坏情况。这些表给出了每个计划的AOQL。破坏性测试使用的计划没有AOQL，因为破坏性测试不能用于筛选被拒绝的批次。 注2: 表中给出的AOQL仅在样本相对于批次较小时才严格正确。如果不是这样，则正确的AOQL将小于列表中的值。将表格中的值乘以以下等式，即可获得正确的值: 5.14 如果进货批次的质量比AQL质量差得多，则纠正检验将大大增加检验成本。 5.15 仅当买方要求时，才使用校正检查。

1.1 This guide provides sampling plans that are intended for use in the inspection of metallic and inorganic coatings on products for the purpose of deciding whether submitted lots of coated products comply with the specifications applicable to the coating. 1.2 The sampling plans are variables plans. In plans of this type, several articles of product are drawn from a production lot. A characteristic of the coating on the drawn articles is measured. The values obtained are used to estimate the number of articles in the lot that do not conform to a numerical limit, for example a minimum thickness. The number is compared to a maximum allowable. 1.3 Variables plans can only be used when the characteristic of interest is measurable, the test method gives a numerical measure of the characteristic, and the specification places a numerical limit on the measured value. It is also necessary that the variation of the characteristic from article to article in a production lot be normally distributed (see Appendix X2 ). Each article must be tested in the same way (for example, coating thickness must be measured at the same location, see X2.7 ) so that the values from article to article are comparable. If one or more of these conditions are not met, a variables plan cannot be used. Instead, an attributes plan must be used. These are given in Guide B602 and Guide B697 . 1.4 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 appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 Sampling inspection permits the estimation of the overall quality of a group of product articles through the inspection of a relatively small number of product articles drawn from the group. 5.2 The specification of a sampling plan provides purchasers and sellers a means of identifying the minimum quality level that is considered to be satisfactory. 5.3 Because sampling plans yield estimates of the quality of a product, the results of the inspection are subject to error. Through the selection of a sampling plan, the potential error is known and controlled. 5.4 Sampling inspection is used when a decision must be made about what to do with a quantity of articles. This quantity may be a shipment from a supplier, articles that are ready for a subsequent manufacturing operation, or articles ready for shipment to a customer. 5.5 In sampling inspection, a relatively small number of articles (the sample) is selected randomly from a larger number of articles (the inspection lot); the sample is inspected for conformance to the requirements placed on the articles. Based on the results, a decision is made whether or not the lot conforms to the requirements. 5.6 Since only a portion of a production lot is inspected, the quality of the uninspected articles is not known. The possibility exists that some of the uninspected articles are nonconforming. Therefore, basic to any sampling inspection plan is the willingness of the buyer to accept lots that contain some nonconforming articles. The number of nonconforming articles in accepted lots is controlled by the size of the sample and the criteria of acceptance that are placed on the sample. 5.7 Acceptance sampling plans are used for the following reasons: 5.7.1 When the cost of inspection is high and the consequences of accepting a nonconforming article are not serious. 5.7.2 When 100 % inspection is fatiguing and boring and, therefore, likely to result in errors. 5.7.3 When inspection requires a destructive test, sampling inspection must be used. 5.8 In acceptance sampling by variables, the coating characteristic of each article in the sample is measured. Using the arithmetic mean of these values, the standard deviation of the process, and the factor k that is found in the Tables, a number is calculated (see 9.3 ). If this number equals or exceeds the specified minimum, the inspection lot conforms to the requirements. If it is less, the lot does not conform. If the standard deviation of the process is not known, the standard deviation of the sample is calculated and used. 5.9 The use of a sampling plan involves the balancing of the costs of inspection against the consequences of accepting an undesirable number of nonconforming articles. There is always a risk that a random sample will not describe correctly the characteristics of the lot from which it is drawn, and that an unacceptable lot will be accepted or an acceptable lot will be rejected. The larger the sample, the smaller this risk but the larger the cost of inspection. 5.10 To understand the risks, consider that if every article in an inspection lot conforms to its requirements, every article in the sample will conform also. Such lots will be accepted ( Note 1 ). If only a few articles in an inspection lot are nonconforming, the sample probably will indicate that the lot is acceptable; but there is a small probability that the sample will indicate that the lot is unacceptable. The larger the proportion of nonconforming articles in an inspection lot, the more likely it will be that the sample will indicate that the lot is unacceptable. If every article in an inspection lot is nonconforming, a sample will always indicate that the lot is unacceptable. Note 1: Throughout this method, it is assumed that no mistakes are made in sampling, measurement, and calculation. 5.11 The probability of accepting an inspection lot that contains nonconforming items is often described in terms of the Acceptable Quality Level (AQL) and the Limiting Quality Level (LQL). The AQL is the quality level that is considered to be acceptable. The LQL is a quality level that is considered to be barely tolerable. A sampling plan is selected that has a high probability of accepting lots of AQL quality and of rejecting lots of LQL quality. In this method, the AQL given for a sampling plan is the quality level of lots (expressed as the percentage of nonconforming articles) that have a 95 % probability of being accepted. The LQL is the quality level of lots that have a 10 % probability of being accepted or, in other words, a 90 % probability of being rejected. The tables in this method give the AQL and LQL of each plan. They also give the 50/50 point, the quality level of a lot that is just as likely to be accepted as rejected. 5.12 The disposition of nonconforming inspection lots is beyond the scope of this method because, depending on the circumstances, lots may be returned to the supplier, kept and used, put to a different use, scrapped, reworked, or dealt with in some other way. An alternative is rectifying inspection in which rejected lots are screened and used. 5.13 In rectifying inspection, when an inspection lot is rejected, all of the articles in the lot are inspected and nonconforming ones are removed. They may be replaced with conforming articles. The now 100 % conforming lot is accepted. With this practice, the average quality level for a series of lots taken as a whole will be better because of the addition of the 100 % conforming lots. When the incoming lots are of a good quality level, the average quality level of a series of lots will be even better when the rejected lots are screened and resubmitted. When incoming lots are of a poor quality level, the average quality of a series of accepted lots will again be good because many of the incoming lots will be rejected and upgraded. At intermediate quality levels of incoming lots, the average quality level of a series of accepted lots will again be improved, but it will not be improved as much as in either of the above cases; and there will be an intermediate quality level where the degree of improvement is the least. This improved quality level is called the Average Outgoing Quality Limit (AOQL). It is the worst condition that can occur under rectifying inspection. The tables give the AOQL for each plan. There is no AOQL for the plans used with destructive tests because destructive tests cannot be used to screen rejected lots. Note 2: The AOQLs given in the tables are strictly correct only when the sample is small with respect to the lot. If this is not the case, the correct AOQL will be smaller than the tabulated value. The correct values are obtained by multiplying the tabulated values by the following equation: 5.14 Rectifying inspection will substantially increase the cost of inspection if the incoming lots are much worse than AQL quality. 5.15 Rectifying inspection is used only when required by the purchaser.