| Connect Follow us on Twitter Like us on Facebook
About | Subscribe | Advertise


Get on-line education from the Pro Video Learning Series.

Problem Solving Forum

| More

July 1 - July 7, 2013

Why would a pull-off adhesion test give a high value (no failure) for a solventless epoxy that later showed poor adhesion in service?

More items for Quality Control

Selected Answers

From Mike Moran of Kiewit Power Enbgineers on August 15, 2013:
Thick epoxy coatings have lateral strength/self supporting. The epoxy can be disbonded; however, it takes a lot of force to break the coating with the pull-off.

From S. Matsumoto of Abraco on August 14, 2013:
Solventless epoxy coatings shrink about 5% when cured. The relationship between WFT and DFT shows this easily. If the coating's adhesion is not resistant to shrink tension, detachment could occur.

From PARVEZ SHAIKH of SANDVIK ASIA PVT. LTD. on August 1, 2013:
When it comes to service, the question involves the exposure condition to which the coating was exposed. Was the coating designed for that exposure?  If not, the chance of failure is very high.  To clarify, we have to get the data detailing the exposure conditions.

From leoncio ucancial of hempel-glucom on July 6, 2013:
The first point is to evaluate the conditions of surface preparation. If the structure will be in immersion service,  surface preparation should be SSPC-SP 5, with a profile of 3 mils mínimum. If the environment i satmospheric, surface preparation should be SSPC-SP 6 or SP10, with a profile of 1.5 to 2.5 mils.

The second point involves the coating systems. Failure of the adhesión could be caused by improper mixing (resin mixing ratio-catalyst).

 The third point is  evaluating the climatic conditions where this painting occurred and evaluating the adhesión test. It should be noted that with epoxy resins at low temperatures, the chemical reaction is slower

From Bonny Njimogu of Construction Specialist Services Ltd. on July 3, 2013:
There could be two major reasons that result in such failures. 1)The tack or primer coat was not applied to the substrate prior to applying the topping. 2) The water level below the substrate might be low during the installation and testing period. Moisture absorption and capillary action at the high water level could affect the substrate, thereby resulting in failure.

From Stefan Danek of Defence Scienece technology Organisation on July 2, 2013:
First, one has to consider whether the pull-off adhesion test was carried out on the same sample that failed later in service, i.e., is the test sample representative of the in-service coating? This will address the very valid point raised by Atanas on whether there is likely to have been a difference in surface preparation (surface preparation and substrate cleanliness, including soluble salts) and paint application (paint sample, operator, equipment, application conditions, DFT, dew point, etc.) If the test sample is not representative of the in-service sample, then there could be any of a number of reasons for the difference as discussed above. Second, in the laboratory, the results obtained from dry adhesion tests can often be superior to wet adhesion tests. Typically, this involves cross hatch testing rather than pull-off adhesion testing, and is used  for coating systems that are relatively thin (less than 5 mils), for example, as applied in the aerospace industry. This can be very critical for exterior coatings exposed to weather, particularly when substrates can be subjected to periods of prolonged wetness. By dry adhesion, I mean undertaking the adhesion test after the coating has cured under standard conditions. Wet adhesion refers to adhesion tests undertaken on the cured paint film following immersion in water. Some specifications require adhesion to be remeasured following immersion in water at ambient temperature for 24 hours. I prefer immersion in water at 122 F (50 C) for 7 days. Coatings will fail wet adhesion tests if they are either unsuited to the application or have been applied over substrates which  contain soluble surface salts which can lead to osmotic blistering, even in epoxy systems applied at 6 -8 mils. The question is what to what climatic conditions was the failed sample exposed in service?

From Atanas Cholakov of ACT on July 1, 2013:
If the test is carried out on a test panel, is the coating been applied in  the same climatic conditions as on the work piece? Often, there is a difference. A pull-off on the work piece itself can give a better indication of adhesion. Coating  application might have been compromised (surface profile, cleanliness). Is the coating being properly selected for the service environment and conditions, and what does 'later' mean in elapsed service life?

Please sign in to submit your answer this question    

Tagged categories: Adhesion; Performance testing; Solvents

Current PSF Question | Submit a PSF Question | Full PSF Archive

KTA-Tator, Inc. - Corporate Office
KTA-Tator EH&S Services

• Ambient & Worker Exposure Air Monitoring
• Safety & Health Program Development
• Lead Paint Assessments
& Specifications
• Health Hazard & Jobsite Safety Assessments
Call 1-800-245-6379

Fischer Technology Inc.
Measure TSA Coatings on Stainless Steel

The PHASCOPE® PMP10 from FISCHER precisely measures thermally sprayed aluminum (TSA) on stainless steel.

Elcometer, Inc.
Durability & Design meet
Performance & Reliability

Elcometer 319 Dewpoint Meter
View the technical data on the Elcometer Dewpoint meter.

HoldTight Solutions Inc.

Our HoldTight®102 salt remover & flash rust preventer prevents flash
rust by removing surface contaminants. It has no equal; only wannabees.
Contact us for your
nearest distributor.
(800) 319.8802

DeFelsko Corporation
PosiTest Automatic Adhesion Tester

Electronically controlled hydraulic pump applies smooth and continuous pull-off pressure at user selectable rates. No twisting, pumping or cranking.

Minerals Research & Recovery

Sharpshot®XL is a new fast-cutting, low-dusting, cost-effective iron silicate abrasive. Call Patrick Conry: 502-552-5895 for details.

SAFE Systems, Inc.
Enduroguard -
The Tough Cable
for a Tough Industry.

Reduce maintenance costs and down time, increase job site safety with Enduroguard Cable. Available exclusively from SAFE Systems. UL listed, flexible, abrasion resistant and cut resistant.

The one way to control
a tank: DRYCO

Temporary climate control equipment. Dehumidifiers,
Heaters, A/C, Power, More…
Call: 866-379-2600

Avalotis Corporation
Choose experience. Choose quality. Choose safety.

Avalotis Corporation has been meeting and exceeding clients’ specifications and expectations for almost 50 years. The first name in painting and protective coatings: Avalotis.

CS Unitec
Peening Preparation Tools

CS Unitec’s hand-held scarifiers are an ideal alternative to small-area shot blasting for cleaning and preparing concrete & metal surfaces.

Technology Publishing

The Technology Publishing Network

The Journal of Protective Coatings & Linings (JPCL) PaintSquare
Durability + Design Paint BidTracker

EXPLORE:      JPCL   |   PaintSquare News   |   Interact   |   Buying Guides   |   Webinars   |   Resources   |   Classifieds
REGISTER AND SUBSCRIBE:      Free PaintSquare Registration   |   Subscribe to JPCL   |   Subscribe to PaintSquare News
MORE:      About   |   Privacy policy   |   Terms & conditions   |   Site Map   |   Search   |   Contact Us

© Copyright 2000-2015, Technology Publishing / PaintSquare, All rights reserved
2100 Wharton Street, Suite 310, Pittsburgh PA 15203-1951; Tel 1-412-431-8300; Fax 1-412-431-5428; E-mail