February 13 - February 19, 2012
How do you adequately assess the adhesion of a newly applied coating?
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Kumar Kolur Vadivelu of Intertek-Moody International-UAE on
March 25, 2012:
The query was not clear to understand. My opinion is that we can use the following method to evaluate the adhesion value of the freshly applied coating. First, ensure the degree of curing of the coating by the solvent rub test; then, we can adopt ASTM D4541 Dolly Pull off or ASTM D3359 method A/B.
M Ehab of North Valley on
March 26, 2012:
In general, for easy site testing: 1. Coat by coat apply cross-cut test (ISO 2409 or ASTM D3359); 2. For final test, apply pull off test (ISO 4624 or ASTM D4541).
Steve Stroud of Stroud Estimating, LLC on
March 2, 2012:
The question is very vague! But tests have been devised, over the years, that will allow adequate testing to be performed. And they have certainly become more reliable as technology has expanded. Whether it is a "bendable pipe" coating, epoxy on CMU in the bathrooms, or a steel girt on the Golden Gate Bridge, its hard to beat the simplicity and accuracy of a dolly pull. Yes, the dolly test is somewhat destructive, but I believe that the accuracy of testing on the actual substrate far outweighs the touch-up that the dolly pull will create. It's not like we are doing a "pull test" on the hood of a new Cadillac!
Albert Holder of NSWC on
February 20, 2012:
Method for Specific Bendability of pipeline coatings: Apply coating on a thin similar substrate, allow 48 hours to fully cure at room temperature. Bend over a 1/8" mandrel rod swiftly. Check for cracking.
Patrick Kennerson of Pacific Coatings Consultants on
February 15, 2012:
The aforementioned tests are the best ones, but this should be done on a sample test plate that is the same substrate and same application process, so as to not damage the new coatings.
Jacek Bordzilowski of CES on
March 5, 2012:
It is essential to check that the coating is fully cured and dried. Multi-layer coatings often have the midcoat not quite dried. The method used depends on the substrate and the coating thicknesses. For a thin steel substrate (below 5 mm) and thin coatings (less than 250 micrometers), the cross-cut knife test give the best results. The X cut test is best thin steel substrates and thicker coatings (over 250 micrometers). The pull-off test is the best for thick steel substrates (over 5 mm) and for every coating thickness.
SANJAY CHOWDHURY of BERGER PAINTS INDIA LIMITED on
February 13, 2012:
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There are three methods for determining the adhesion of newly applied coatings. They are 1) pull-off adhesion test, which is also known as dolly test as per ASTM D 4541 for metal substrates, and for concrete, ASTM D 7234; 2) cross cut tape test for adhesion, which covers procedures for assessing the adhesion of coating film to metallic substrates by applying and removing pressure-sensitive tape over cuts made in the film as per ASTM D 3359; 3) cross-cut knife test, which uses a knife to cut the film at a 30- to 45-degree angle in the form of a X and observe the adhesion as per ASTM D 6677.
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