SSPC PA 9-2018

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SSPC-PA 9

July 20, 2015

Editorial revisions August 8, 2015 and February 12, 2018

SSPC: The Society for Protective Coatings

PAINT APPLICATION SPECIFICATION NO. 9

Measurement of Dry Coating Thickness

Using Ultrasonic Gages

1. Scope

1.1 This standard describes procedures to measure the

thickness of dry, homogeneous coatings applied on a variety of

surfaces such as concrete, wood, wallboard, plastic, ber and

composite material using commercially available ultrasonic

coating thickness gages. These procedures are intended

to supplement manufacturers’ operating instructions for the

manual operation of the gages and are not intended to replace

them.

1.2 The procedures for calibration, adjustment, and

general use of ultrasonic coating thickness gages are

described in ASTM D6132 and the gage manufacturer’s

instructions. This document focuses on the correct method for

taking measurements.

1.3 Current ultrasound technology may not be capable of

accurately measuring the DFT of some coatings (see Notes

9.1 and 9.2).

2. Description

2.1 The procedures described in this standard include

criteria for determining the number of measurements, location

of measurements, and whether the dry lm thickness (DFT) of

the coating conforms to project specications.

2.2 DESCRIPTION OF GAGES: Ultrasonic gages use a

transducer in the probe to send pulses into the coating and

measure the time taken by that pulse to return to the probe tip

to calculate coating thickness (see Note 9.3).

2.3 DEFINITIONS

2.3.1 Gage Reading: A single instrument reading.

2.3.2 Spot Measurement: The average of three or at least

three gage readings made within a 15-cm (6-inch) diameter

circle.

Discussion: Acquisition of more than three gage readings

within a spot is permitted. Any unusually high or low gage

readings that are not repeated consistently are discarded.

The average of the acceptable gage readings is the spot

measurement.

2.3.4 Homogeneous: Of the same or similar in composition

or structure. In this standard, the term “homogeneous coating”

refers to a coating of uniform composition throughout that

does not contain large, solid particles such as sand.

3. References

3.1 The date of the referenced standards in effect at the

time of publication of this standard is shown below. Upon

mutual agreement, the latest revision of a referenced standard

in effect on the date of invitation to bid may be used, provided

it does not change the technical requirements of this SSPC

standard. Standards marked with an asterisk (*) are referenced

only in the Notes, which are not requirements of this standard.

3.2 If there is a conict between the requirements of

any of the cited referenced standards and this standard, the

requirements of this standard shall prevail.

3.3 ASTM INTERNATIONAL STANDARDS1

* D1005-95(2013) Standard Test Method for Measure-

ment of Dry-Film Thickness of Organic

Coatings Using Micrometers

* D4138-07a(2013) Standard Test Methods for Measure-

ment of Dry Film Thickness of

Protective Coating Systems by

Destructive, Cross-Sectioning Means

* D4414-95(2013) Standard Practice for Measurement of

Wet Film Thickness by Notch Gages

D6132-13 Standard Test Method for Nonde-

structive Measurement of Dry Film

Thickness of Applied Organic Coatings

Using an Ultrasonic Coating Thickness

Gage

* D7091-13 Standard Practice for Nondestructive

Measurement of Dry Film Thickness

of Nonmagnetic Coatings Applied to

Ferrous Metals and Nonmagnetic,

Nonconductive Coatings Applied to

Non-Ferrous Metals

3.4 SSPC STANDARDS

* SSPC-PA 2(2015) Procedure for Determining Confor-

mance to Dry Coating Thickness

Requirements

1 ASTM International, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, phone

int+1-610-832-9500. For referenced ASTM standards, visit the ASTM website <http://www.

astm.org>

SSPC-PA 9 was rst issued in April 2008, and was revised in July 2015, with editorial

revisions issued in August 2015 and February 2018.

SSPC-PA 9

July 20, 2015

Editorial revisions August 8, 2015 and February 12, 2018

4. Gage Requirements

The ultrasonic gage shall be capable of measuring the

thickness of a coating over a non-metallic substrate. To qualify

under this standard, the gage shall have a minimum accuracy

within ±5 percent. All gages shall be calibrated and adjusted

following the manufacturer’s instructions and be in accordance

with ASTM D 6132.

5. Calibration and Verication of Accuracy

5.1 ASTM D6132 describes three operational steps

necessary to ensure accurate coating thickness measurement:

calibration, verication of accuracy and adjustment of coating

thickness measuring gages, as well as proper methods for

obtaining coating thickness measurements. These steps shall

be completed before taking coating thickness measurements to

determine conformance to a specied coating thickness range.

Verication of accuracy shall be performed in accordance with

ASTM D6132.

5.2 Gages shall be calibrated by the equipment

manufacturer, its authorized agent, or an accredited calibration

laboratory. A test certicate or other documentation showing

traceability to a national metrology institution is required.

There is no standard time interval for re-calibration, nor is

one absolutely required. Calibration intervals are usually

established based upon experience and the work environment,

or when specied. A one-year calibration interval is a typical

starting point suggested by gage manufacturers.

5.3 To guard against measuring with an inaccurate gage,

gage accuracy shall be veried according to the procedures

described in ASTM D6132. Verication shall be performed, at

minimum, at the beginning and end of each work shift. The

user is advised to verify gage accuracy during measurement

acquisition (e.g., hourly) when a large number of measurements

are being obtained. If the gage is dropped or suspected of

giving erroneous readings during the work shift, its accuracy

shall be rechecked.

5.4 Record the serial number of the gage, the reference

standard used, the stated thickness of the reference standard

as well as the measured thickness value obtained, and the

method used to verify gage accuracy. If the same gage,

reference standard, and method of verication are used

throughout a job, the information need be recorded only once.

The stated value of the standard and the measured value shall

be recorded each time accuracy is veried.

5.5 If the gage fails the post-measurement accuracy

verication check, all measurements acquired since the

last accuracy verication check are suspect. In the event of

physical damage, wear, or high usage, or after an established

calibration interval, the gage shall be rechecked for accuracy

of measurement. If the gage is not measuring accurately, it

shall not be used until it is repaired and/or recalibrated (usually

by the gage manufacturer).

6. Measurement Procedures

6.1 Verify that the gage will provide accurate readings of

the coating to be measured, using the procedure in Note 9.2.

6.2 NUMBER OF READINGS: Repeated gage readings,

even at points close together, often differ due to small surface

irregularities of the coating and the substrate (see Notes 9.4

and 9.5). Therefore, a minimum of three (3) gage readings

shall be made for each spot measurement of the coating. For

each new gage reading, move the probe to a new location

within the 15-cm (6-inch) diameter circle dening the spot.

Each gage reading shall be at least 5 cm (2 inches) from the

other gage readings. Discard any single unusually high or low

gage readings that are not repeated consistently. The average

of the acceptable gage readings is the spot measurement. See

Note 9.6 regarding removal of couplant after completing spot

measurements.

6.3 NUMBER OF MEASUREMENTS: Unless otherwise

specied in the procurement documents (project specication),

an area measurement is obtained by taking ve (5) separate

spot measurements (average of the gage readings,

described in Section 6.2) randomly spaced throughout each

10-m2 (approximately [~] 100-ft2]) area to be measured

and representative of the coated surface. The ve spot

measurements shall be made for each 10-m2 (~100-ft2) area

as follows:

6.3.1 For areas of coating not exceeding 30 m2 (~300 ft2)

in area, each 10-m2 (~100 ft2) (or increment thereof) area shall

be measured.

6.3.2 For areas of coating greater than 30 m2 (~300 ft2)

in area and not exceeding 100 m2 (~1,000 ft2) in area, three

10-m2 (~100-ft2) (or increment thereof) areas shall be arbitrarily

selected by the inspector and measured.

6.3.3 For areas of coating greater than 100 m2 (~1000 ft2)

in area, the rst 100 m2 (~1000 ft2) shall be measured as stated

in Section 6.3.2. For each additional 100-m2 (~1000-ft2) coated

area (or increment thereof), arbitrarily select and measure one

10-m2 (~100-ft2) area.

6.4 NONCONFORMING AREAS: If the coating thickness

for any 10-m2 (~100-ft2) area is not in compliance with the

contract documents, the procedure described here shall

be followed to assess the magnitude of the nonconforming

thickness.

6.4.1 Determine the spot DFT at 1.5-m (5-ft) intervals in

eight equally spaced directions radiating outward from the

nonconforming 10-m2 (~100-ft2) area. If there is no place to

measure in a given direction, then no measurement in that

direction is necessary. Acquire spot measurements in each

direction (up to the maximum surface area coated during the work

shift) until two consecutive conforming spot measurements are

acquired in that direction or until no additional measurements

SSPC-PA 9

July 20, 2015

Editorial revisions August 8, 2015 and February 12, 2018

are possible. Acceptable spot measurements are dened by

the minimum and maximum values in the contract documents.

No allowance is made for variant spot measurements, as is the

practice when determining the area DFT. An illustration of this

procedure is shown in Figure 1.

6.4.1.1 On complex structures or in other cases where

making spot measurements at 1.5-m (5-ft) intervals is not

practical, spot measurements shall be performed on repeating

structural units or elements of structural units. This method

shall be used when the largest dimension of the unit is less than

3 m (10 ft). Make spot measurements on repeating structural

units or elements of structural units until two consecutive units

in each direction are conforming or until there are no more

units to test.

6.3.2 Non-compliant areas shall be demarcated using

removable chalk or other specied marking material and

documented. All of the area within 1.5 m (5 ft) of any

non-compliant spot measurement shall be designated as

non-compliant. For a given measurement direction or unit

measurement, any compliant area or unit preceding a

non-compliant area or unit shall be designated as suspect, and

as such is subject to re-inspection after corrective measures

are performed (see Note 9.7).

7. Conformance to Specied Thickness

7.1 A minimum and a maximum thickness are normally

specied for each layer of coating. If a single thickness value

is specied and the coating manufacturer does not provide

a recommended range of thickness, then the minimum and

maximum thickness for each coating layer shall be ± 20

percent (%) of the stated value.

7.2 Table 1 provides four thickness restriction levels.

Level 1 is the most restrictive and does not allow for any

deviation of spot or area measurements from the specied

minimum and maximum thickness, while Level 4 is the least

restrictive. Depending on the coating type and the prevailing

service environment, the specier selects the dry lm thickness

restriction level for a given project. If no restriction level is

specied, then Level 3 is the default. It is possible to specify

a maximum thickness threshold for Level 4 Spot or Area

measurements for some generic product types and service

environments.

7.3 For the purpose of nal acceptance of the total dry lm

thickness, the cumulative thickness of all coating layers shall be

no less than the cumulative minimum specied thickness and

no greater than the cumulative maximum specied thickness.

8. Disclaimer

8.1 While every precaution is taken to ensure that all

information furnished in SSPC standards is as accurate,

complete and useful as possible, SSPC cannot assume

responsibility nor incur any obligation resulting from the use of

any materials, coatings or methods specied therein, or of the

standard itself.

FIGURE 1

DETERMINING EXTENT OF NONCONFORMING AREAS

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摘要：

SSPC PA 9-2018是由美国防护涂料协会（SSPC）发布的关于涂装检验中干膜厚度现场测量的标准规范。该标准详细规定了在钢结构及其他工业涂装项目中，使用磁性或非磁性测厚仪进行干膜厚度测量的方法、步骤、设备校准及数据记录要求，旨在确保涂层厚度均匀性符合项目技术规范。SSPC PA 9-2018取代了旧版标准，增加了对统计过程控制的引用，并强调了测量点数量、位置选择以及如何评估测量结果的可接受性。对于从事涂料施工、检验及质量控制的专业人员而言，掌握该标准有助于提高涂层耐久性、减少返工风险，并有

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SSPC PA 9-2018

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