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May 20 - May 24, 2019

How do you accurately measure the adhesion of inorganic zinc?

Selected Answers

From Larry Muzia of Exceletech Coating & Applications, LLC on May 31, 2019:
Inorganic zincs have a tendency to be self-inspecting, meaning if there is a problem, it will typically show up early in the life cycle; however, this does not to mean that quality assurance is unimportant. Using a 20-mm dolly and applying a thin layer of glue to the dolly itself is a suitable method. Making an X-cut through the zinc metal is not totally accurate; however, it will give a subjective indication of the adhesion I personally would use a dull scraper to break the plane of the coating at the cut edges for an idea of potential go/no go issues. Inorganic zinc has poor tensile strength and will not achieve the same psi of adhesion as, say, a 5-mil epoxy, which is why proper curing and surface cleanliness and profile are critical to longevity.

From Ricardo Márceles of Pintuco on May 23, 2019:
What value (psi) does that test give you?

From Paul Tsourous of Jupiter on May 23, 2019:
An "Old School" subjective method of spot-checking adhesion would be to take a nickel coin and place it on its side against the coated surface, exert downward pressure, and run it across the coated surface. If the result is a thin, shiny line, it would be considered adherent. If the IOZ surface appeared to have rough, cracked edges along the line, then there is a adhesion issue.

From Ricardo Márceles of Pintuco on May 22, 2019:
The tests by direct traction with epoxy adhesives or mono- components are not recommended because of the porosity of the zinc, which does not allow good security. For  thicknesses less than 4 mils, it is more advisable to make tests by X cut, or even the test with the coin, dragged at 45 ° on the zinc rich. It must resist drag.

From Janssen Christophe of Lassarat on May 22, 2019:
I personnaly use a pull-off test, with époxy glue to make sure that the glue (like cyanoacrylate) does not penetrate the paint film and disturb the result of the test.

From Duane Cooper of BAE Systems Ship Repair on May 21, 2019:
Use a pull test.

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Tagged categories: Coating Materials; Zinc; Zinc-rich (inorganic)

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