SSPC-PA 2 - Measurement of Dry Coating Thickness with Magnetic Gages

Sep 22, 2026

SSPC-PA 2 specifies procedures for calibrating and measuring dry coating thickness (DFT) on ferrous and non-ferrous metal substrates using nondestructive magnetic and eddy current gages. It defines spot measurement and spot selection rules across 10 m2 (100 ft2) areas, including averaging requirements, maximum allowable values, and handling of unusually high or low readings. It also details gage types (Type 1 pull-off and Type 2 constant pressure), rechecking during work shifts, and surface preparation for dirty, tacky, or soft films.

LanguageEnglish

CategoryPaper Templates

FormatPDF

Pages5

Reading Time2 min

AccessFree to download

Spot Measurement

Calibration and Verification During Work Shifts

Maximum Thickness and Area Averaging

Alloy Steel Substrates Considerations

Continue Sspc pa2 2018 pdf file download 2018 2.1.2 Spot Measurement: The average of at least three gage readings made within a 1.5 inch (4 cm) diameter circle. (See Section 8.15. ) The standards must be large enough to exceed the critical mass of steel needed to satisfy the magnetic field of the Type 1 (pull-off) magnets. Manufacturers’ literature may be consulted to determine if higher maximum thickness readings are allowable under specific circumstances. The scale is nonlinear. During the work shift, if the gage is dropped or suspected of giving erroneous readings, its calibration should be rechecked. SSPC PA 2 describes a procedure for determining shop or field conformance to a specified coating dry film thickness (DFT) range on ferrous and non-ferrous metal substrates using nondestructive coating thickness gages (magnetic and eddy current) described in ASTM D7091 . In a Type 16 “pencil” gage, a calibrated coil spring measures the force necessaryto pull the permanent magnet from the surface. Some gages have three separate indicators which compensate for horizontal, vertical and overhead positions. 2 COPYRIGHT Steel Structures Painting Council Licensed by Information Handling Services SSPC-PA 2 June 1.1996 5.1.4 If the dry film thickness for any 1O m2 (1O0 ft2) area (see Sections 5.1.2 and 5.1. 3) is not in compliance with the requirements of Sections 5.2.1 and 5.2.2, then additional measurements must be made to isolate the non-conforming area. 5 pm (0 .1 mil) . Now its calibration over blastcleanedsteel mustbe verified. This is allowed becauseonly the average of the three readings(¡ .e., the spot measurement) must be greaterthan orequal to 51 pm. Moreover, SSPC does not issue interpretations of its specifications, guides or recommendations; and no person is authorized to issuean interpretation ofanSSPC specification,guideorrecommendationonbehalf of SSPC. Whenthe magnet is brought near steel, the magnetic flux density within the magnet is increased. Unusually soft films may be dented by the pressure of the probe. (See Section 4.3. ) If a Type 1 gage is used, the coating thickness is obtained by subtracting the base metal reading. Although 53 pm isbelow the specified minimum, it is still within 80 percent of it, so the specificationis satisfied. Internal balancing mechanisms in most banana gages compensate for horizontal, vertical and overhead positions so that there is no need to recalibrate when changing orientation. Note the gage is not to be calibrated on the bare substrate. Nosingle spot measurement in any 1O m2(100 ft2)area shall be morethan 120% of the specified maximum thickness. 8.6ALLOY STEEL SUBSTRATES: Differences among most mild low-carbon steels will not significantly effect magnetic gage readings. Also, residual magnetism in the steel substrate may affect gage readings. Take the average of the acceptable gage readings as the spot measurement. Eighty percentof 64 pmis 51 pm (0 .80 x 64 = 51) . 5.2.2 Maximum Thickness: The average of the spot measurements for each 10 m2 (100 ft2) area shall not be more than the specified maximum thickness. Eighty percent of 2.5 mils is 2.0 mils (0 .80 x 2.5 = 2.0) . 8.1.2 Type 2 (constant pressure probe) gages operate on two different magnetic principles. Record the calibration data and the method used to verify the calibration. Shims of sheet plastic or ofnon-magnetic metals, which are permissible for calibrating Type 2 (constant pressure probe) gages, should not be used for calibration of Type 1 gages. However, the response of these elements is temperature dependent, so temperature compensation is required. Notes Notes are not requirements of this standard. 2. If a maximum thickness value is not explicitly specified, the specified thickness shall be the minimum. 2 Measurement of Dry Coating Thickness with Magnetic Gages 1. Discard any unusually high or low gage reading that cannot be repeated consistently. With a correctly calibrated and adjusted Type 2 gage, the reading o

FAQs

What is spot measurement in SSPC-PA 2?

Spot measurement is the average of at least three gage readings taken within a 1.5 inch (4 cm) diameter circle.

How are additional measurements triggered when results do not comply?

If the dry film thickness for any 10 m2 (100 ft2) area is not in compliance with the applicable requirements, additional measurements must be made to isolate the non-conforming area.

What conditions must be met to measure accurately with magnetic gages?

The probe and coating surface must be free from dust, grease, and other foreign matter to ensure close contact and avoid adhesion of the magnet.

Sep 22, 2026

Upload by Theodore