ASTM B762 - 21

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Designation: B762 −21
Standard Guide of
Variables Sampling of Metallic and Inorganic Coatings
1
This standard is issued under the ﬁxed designation B762; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
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 appro-
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.5 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.
2. Referenced Documents
2.1 ASTM Standards:
2
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
2.2 ANSI Standards:
3
ANSI/ASQC Z1.9-1979 Sampling Procedures and Tables
for Inspection by Variables for Percent Non-Conformance
ANSI/ASQC Z1.4-1981 Sampling Procedures and Tables
for Inspection by Attributes
2.3 Military Standards:
4
MIL-STD-105 Sampling Procedures and Tables for Inspec-
tion by Attributes
MIL-STD-414 Sampling Procedures and Tables for Inspec-
tion by Variables for Percent Defective
3. Terminology
3.1 destructive test, n—test that destroys the tested article or
makes it nonconforming to a requirement.
3.2 inspection lot, n—collection of articles of the same kind
that is submitted to inspection for acceptance or rejection as a
group.
3.3 nondestructive test, n—test that neither destroys the
tested article nor makes it nonconforming to a requirement.
3.4 sample, n—articles randomly selected from an inspec-
tion lot whose quality is used to decide whether or not the
inspection lot is of acceptable quality.
3.5 standard deviation, n—measure of dispersion equal to
the square root of the mean of the squares of the deviations
from the arithmetic mean of the distribution (see 9.2.6).
4. Summary of Guide
4.1 The plans in this guide provide the same protection as
the attributes plans in Tables 1, 2, and 3 of Guide B602 and are
1
This guide is under the jurisdiction of ASTM Committee B08 on Metallic and
Inorganic Coatings and is the direct responsibility of Subcommittee B08.10 on Test
Methods.
Current edition approved Oct. 1, 2021. Published November 2021. Originally
approved in 1986. Last previous edition approved in 2016 as B762 – 90(2016). DOI:
10.1520/B0762-21.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
3
Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org.
4
Available from Standardization Documents Order Desk, DODSSP, Bldg. 4,
Section D, 700 Robbins Ave., Philadelphia, PA 19111-5098.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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.
1

interchangeable with them when the conditions necessary for
variables sampling exist. This method has no plan comparable
to Table 4 of Guide B602, because variables plans are subject
to an excessive probability of error when the number of
nonconforming articles in a lot is expected to be approximately
1 % or less as it is for the Table 4 plan. Also for this reason,
comparable variables plans are not given for the smallest lot
sizes of Tables 1 and 2 of Guide B602. The plans of Table 4,
and Tables 1 and 2 in Guide B602 are described as Level I,
Level II, and Level III, respectively. For consistency, Table 1
and Table 2 of this guide are described as Level II since they
are comparable to Table 1 of Guide B602, and Table 3 and
Table 4 are described as Level III.
4.2 The main advantage of a variables sampling plan over
an attributes plan is that fewer articles need to be inspected to
obtain the same protection. For example, a sample of 12 using
variables can give the same protection as a sample of 50 using
attributes. On the other hand, more expensive test methods may
be required to yield the measurements required by variables
sampling.
4.3 Generally, thickness is the only characteristic of a
coating that meets the conditions of a variables plan given in
1.3. For that reason, the plans in this method are designed to be
used when the speciﬁcation for the characteristic in question is
a minimum value, which is the usual case for coating thickness.
Variables plans can be used when the limit is a maximum and
when there are both a minimum and a maximum. Plans for
these cases are given in the references.
4.4 The sampling plans in Tables 1 and 2 of this guide are
considered to be standard for nondestructive testing and will be
used unless the buyer speciﬁes otherwise. Tables 5 and 6 will
be used for destructive testing; these plans use smaller samples
to reduce the cost of inspection with a resultant reduction of the
ability to distinguish between conforming and nonconforming
lots.
4.5 Additional variables plans are given in Appendix X3.
Also found there are instructions for the calculation of plans for
needs that are not covered.
5. Signiﬁcance and Use
5.1 Sampling inspection permits the estimation of the over-
all quality of a group of product articles through the inspection
of a relatively small number of product articles drawn from the
group.
TABLE 1 Level II—Sampling Plans for Nondestructive Tests,
Standard Deviation Known
A
Inspection
Lot Size nkAQL LQL 50/50
Point AOQL
91 through
280
7 1.664 1.1 12 4.8 2.4
281 through
500
12 1.649 1.7 10 5.0 2.6
501 through
1 200
16 1.712 1.7 8.2 4.4 2.3
1 201 through
3 200
25 1.704 2.1 7.4 4.4 2.5
3 201 through
10 000
36 1.778 2.0 5.9 3.8 2.2
10 001 through
35 000
52 1.829 2.0 4.9 3.4 2.1
Over 35 000 82 1.893 1.9 4.0 2.9 1.9
A
The AQL, LQL, 50/50 Point, and AOQL are in percent.
TABLE 2 Level II—Sampling Plans for Nondestructive Tests,
Standard Deviation Unknown
A
Inspection
Lot Size nkAQL LQL 50/50
Point AOQL
91 through
280
16 1.663 1.0 12 4.8 2.4
281 through
500
29 1.649 1.7 10 5.0 2.6
501 through
1 200
40 1.713 1.7 8.2 4.3 2.2
1 201 through
3 200
61 1.704 2.1 7.4 4.4 2.5
3 201 through
10 000
92 1.778 2.0 5.9 3.8 2.2
10 001 through
35 000
137 1.825 2.0 4.9 3.4 2.0
Over 35 000 223 1.893 1.9 4.0 3.0 1.9
A
The AQL, LQL, 50/50 Point, and AOQL are in percent.
TABLE 3 Level III—Sampling Plans for Nondestructive Tests,
Standard Deviation Known
A
Inspection
Lot Size nkAQL LQL 50/50
Point AOQL
51 through
150
6 1.432 1.8 18 7.6 3.8
151 through
280
10 1.411 2.7 16 7.9 4.1
281 through
500
14 1.470 2.8 13 7.1 3.5
501 through
1 200
23 1.492 3.3 11 6.8 3.8
1 201 through
3 200
30 1.551 3.2 9.4 6.0 3.5
3 201 through
16 000
44 1.618 3.1 7.7 5.3 3.2
16 001 through
35 000
66 1.680 3.0 6.4 4.6 3.0
Over 35 000 103 1.719 3.0 5.6 4.4 2.9
A
The AQL, LQL, 50/50 Point, and AOQL are in percent.
TABLE 4 Level III—Sampling Plans for Nondestructive Tests,
Standard Deviation Unknown
A
Inspection
Lot Size nkAQL LQL 50/50
Point AOQL
51 through
150
12 1.433 1.7 19 7.6 3.8
151 through
280
19 1.410 2.6 16 7.9 3.7
281 through
500
29 1.470 2.8 13 7.1 3.8
501 through
1 200
48 1.494 3.3 11 6.7 3.8
1 201 through
3 200
66 1.551 3.2 9.4 6.0 3.5
3 201 through
16 000
102 1.618 3.1 7.7 5.3 3.2
16 001 through
35 000
159 1.680 3.0 6.4 4.6 3.0
Over 35 000 248 1.717 3.0 5.6 4.3 2.9
A
The AQL, LQL, 50/50 Point, and AOQL are in percent.
B762 − 21
2

5.2 The speciﬁcation of a sampling plan provides purchas-

ers 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 will-

ingness of the buyer to accept lots that contain some noncon-

forming 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 conse-

quences 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 char-

acteristic of each article in the sample is measured. Using the

arithmetic mean of these values, the standard deviation of the

process, and the factor kthat 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 require-

ments. 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 unaccept-

able. 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 % prob-

ability 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 ac-

cepted. 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

TABLE 5 Sampling Plans for Destructive Tests, Standard

Deviation Known

Inspection Lot Size nkAQL LQL 50/50

Point

26 through 1 200 5 1.262 2.3 25 10

1 201 through 35 000 10 1.411 2.7 16 7.9

Over 35 000 14 1.519 2.5 12 6.5

The AQL, LQL, and 50/50 Point are in percent.

TABLE 6 Sampling Plans for Destructive Tests, Standard

Deviation Unknown

Inspection Lot Size nkAQL LQL 50/50

Point

26 through 1 200 9 1.181 2.8 27 12

1 201 through 35 000 19 1.412 2.5 16 7.9

Over 35 000 34 1.497 2.8 12 6.7

The AQL, LQL, and 50/50 Point are in percent.

B762 − 21

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摘要：

ASTM B762 - 21 是一项由美国材料与试验协会发布的最新标准，专门针对镍、钴及其合金粉末的干筛分粒度分布测试方法。该标准规定了使用一系列标准筛网对金属粉末进行粒度分析的具体操作步骤、设备要求及数据报告格式，适用于冶金、增材制造、电池材料及粉末冶金等领域。通过遵循 ASTM B762 - 21，企业能够确保粉末材料的粒度均匀性与工艺稳定性，从而提升最终产品的质量与可重复性。该标准为质量控制、研发及供应链管理提供了统一的测试依据，有助于减少因粒度差异导致的批次间性能波动，是金属粉末行业重要

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