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November 4 - November 8, 2019

Is the MEK rub test a conclusive test to check the cure of IOZ coatings?

Selected Answers

From Tom Schwerdt of Texas Department of Transportation on November 14, 2019:
Jon, be aware that the pencil hardness test is quite variable, and correlation between manufacturers (and even batch to batch) can be poor. ASTM does not have an accepted method for verifying the calibration of pencils for hardness. So, we're left with three common field methods, each with issues. Of the three, I'm most confident in the MEK rub for reproduceability, and many hardware stores carry MEK.

From Geir Christianslund of Aker Solutions MMO on November 13, 2019:
There are many roads that lead to Rome... What's conclusive for any test that an inspector shall perform the test that is acceptable in the procedure and standard that this job shall follow..

From Ronald Lewis of Corrosion Management Ltd. on November 12, 2019:
First, forgive me if it appears that I am boasting, but as an American working for the DIMET COATINGS CO. in Australia, I found I was working for the inventor's for DIMETCOAT Inorganic Zinc Coating. There are several varieties, with air-cured being most preferred. However, during a familiarization tour of the Whyalla Pipeline in South Australia, I saw the first major application for Dimetcote - a moisture-cured zinc coating. Soon thereafter, AMERON became the DIMET USA licensee, with whom I had several Los Angeles visits. AMERON developed the first chemically cured DIMETCOTE 6 product. To my knowledge, all Dimetcoat products were successfully inspected by the coin rub test, using  the edge of the flat side of the coin. Only the chemically cured Dimetcote 6 was more aggressively inspected. 

From Jon Cavallo of Sponge-Jet Inc. on November 8, 2019:
Given my druthers, I would druther use pencil hardness for several reasons, including 1) limiting personnel exposure to MEK for health reasons, 2) limiting use of MEK for safety reasons (flammability, disposal, etc.) and 3) TSA won't let me take MEK through airport security! All of the coating manufacturers that I have dealt with to date will provide me with pencil hardness = cure data for their coatings.

From Bryant Chandler of Greenman-Pedersen, Inc. on November 7, 2019:
IOZ coatings are both solvent- and water based. Problems developed with the water-based coating after both the MEK rub test and coin rub test determined the coating was cured. CCC &L (now GPI Labs) did extensive testing and was able to determine that the water-based coating could resolublize under certain conditions.

From Kalpesh Patel of Endura Manufacturing Co. Ltd. on November 7, 2019:
I agree with Jeff. Curing of IOZ Coating is dependent on moisture, temperature and time. So, uncured IOZ coatings can give you problems, like cohesive break, delamination of topcoat, and zinc splitting. So it is important to make sure IOZ coating is cured properly before applying an intermediate coat or topcoat. Even though MEK rub or coin rub are not conclusive tests,  they are  good tools to determine IOZ coatings' cure and give you at least some confidence.

From Jeff Kim of Sherwin-Williams on November 5, 2019:
I would not call it "conclusive" or indicative of the entire surface coated. When performed properly, the MEK rub test can give you a good indication of cure but only for the specific area tested. The same holds true for the coin test.

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Tagged categories: Curing; Performance testing; Quality Control

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