ASTM D4752-20

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Designation: D4752 − 10 (Reapproved 2015) D4752 − 20
Standard Practice for
Measuring MEK Resistance of Ethyl Silicate (Inorganic)
Zinc-Rich Primers by Solvent Rub
This standard is issued under the fixed designation D4752; 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 practice describes a solvent rub technique for assessing the MEK resistance of ethyl silicate (inorganic) zinc-rich
primers. The MEK resistance of some two-component ethyl silicate zinc-rich primers has been shown to correlate well with the
cure of the primer as determined by diffuse reflectance infrared spectroscopy. The technique can be used in the laboratory, field,
or in the fabricating shop. Practice D5402 is the preferred method for organic coatings.
1.2 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.3 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. Specific hazard statements are given in Section 6. Consult supplier’s Material
Safety Data Sheet(s) for specific hazard information relating to the solvent used.
1.4 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.
2. Referenced Documents
2.1 ASTM Standards:
D740 Specification for Methyl Ethyl Ketone
D4138 Practices for Measurement of Dry Film Thickness of Protective Coating Systems by Destructive, Cross-Sectioning
Means
D5402 Practice for Assessing the Solvent Resistance of Organic Coatings Using Solvent Rubs
D7091 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. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 double rub, n—the act of rubbing a solvent saturated cloth in one complete forward and backward motion over a coated
surface.
4. Significance and Use
4.1 Ethyl silicate zinc-rich primers cure by the reaction of the vehicle with moisture, thereby providing a binder. binder for the
zinc. As relative humidity and temperature vary during the day, vary, so does the rate of cure. A certain minimum degree of cure
is necessary prior to topcoating. It has been shown that the degree of cure of ethyl silicate zinc-rich primers can be measured by
the chemical changes occurring using diffuse reflectance infrared spectroscopy. This solvent rub test has been shown to correlate
well with the infrared spectroscopic results of some two-component ethyl silicate inorganic zinc systems.
This practice is under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings, Materials, and Applications and is the direct responsibility of
Subcommittee D01.46 on Industrial Protective Coatings.
Current edition approved Feb. 1, 2015Feb. 1, 2020. Published February 2015February 2020. Originally approved in 1987. Last previous edition approved in 20102015
as D4752 – 10.D4752 – 10 (2015). DOI: 10.1520/D4752-10R15.10.1520/D4752-20.
Starr, T. L., Henton, L. E., Lewis, W. S., and Rideout, F. A., “Improved Field Reliability of High Performance Coating Systems: Phase II—Develop Procedures and
Criteria in Critical Performance Areas,” available from SSPC: The Society for Protective Coatings, 40 24th St., Sixth Floor, 800 Trumbull Drive, Pittsburgh, PA 15213,15205,
www.sspc.org.
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.
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D4752 − 20
4.2 The degree of cure rating (Resistance Rating in Table 1) required for prior to the application of specific topcoats must be
agreed upon before the practice is used.
5. Reagents and Materials
5.1 Methyl Ethyl Ketone (MEK), in accordance with Specification D740.
5.2 100 % Cotton, Shop Cloth, approximately 300 by 300 mm (12 by 12 in.) contrasting in color to the coatingprimer to be
evaluated.
5.3 Squeeze Bottle.
5.4 Proper Safety Equipment, as determined from the solvent MSDS,SDS, for example, solvent resistant gloves, respirator.
6. Procedure
6.1 Select areas on the primer surface at least 150 mm (6 in.) long on which to run the tests. Clean the surface with tap water
or dry cloth to remove loose material.
NOTE 1—Tap water may influence the cure of the zinc-rich primer.
6.2 Measure the dry film thickness of the primer in the selected areas in accordance with Test Methods Practice D7091 or
Practices D4138. Mark a 150- by 25-mm (6- by 1-in.) rectangular test area on the undamaged cleaned surface using a pencil or
other suitable solvent resistant marker.
6.3 Fold the cloth into a pad of double thickness and saturate it to a dripping wet condition with the methyl ethyl ketone. Do
not allow more than 10 s to elapse before proceeding to the next steps.
6.4 Place the properly protected index finger into the center of the pad while holding excess cloth with the thumb and remaining
fingers of the same hand. With the index finger at a 45° angle to the test surface, rub the rectangular test area with moderate
pressure first away from the operator and then back towards the operator. Complete each double rub (one forward and back motion)
in about 1 s.
6.5 Continue rubbing the surface with the MEK saturated pad, wetting the pad as necessary without lifting it from the surface,
until either the metal substrate is exposed or 50 double rubs have been completed. If the former, record the number of rubs when
the substrate is exposed.
6.6 Select an adjacent area to be used as a control. Repeat 6.1 – 6.5, except use a dry cloth to establish the effect of burnishing
without the influence of MEK. Use this area as the control to visually show the appearance of No Effect.
6.7 Inspect the test areas and the cloths. Rate the results in accordance with Table 1.
7. Report
7.1 Report, as a minimum, the follo
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