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Question posted - July 8 to July 14, 2013:

For coatings with a high-solids content (95% or more), what kinds of defects, such as holidays or micropores, are possible or likely to occur in the applied film? How can these be prevented or remedied?


Selected Answers

From Steve Brunner of WPC Technologies on October 16, 2013:

Most of the problems seen in high solids coatings are a result of application. The coatings are designed with flow additives to aide in application but good techniques are needed. Gone are the days of adding additional solvent to help. These high solid coatings can orange peel when air pressure is too high, the gun is too close to the surface or, with airless spraying, when the pressure is too high. These fixes are somewhat easy to resolve. With pinholing of the coating during application, heated airlines may be used to make the coating more fluid and fill in these voids. One should verify with the tech data sheet the temperature that is acceptable. 

From vikraman govindraj of Rigmetals L.L.C on October 14, 2013:
For high-solid and high-dry-film thickness coating, holidays and pinholes are likely defects. For paints with solids content higher than 95%, mixing should be proper, pump ratio needs to be adequate, pump should have slow moving piston, tip sizes need to be appropriate,  and airless spray operator need to be skilled.

During application, the applicator needs to make cross passes, one pass right to left and the next pass up and down. Proper stripe coating on weld seams and difficult-to-access areas is a must. As usual, proper surface preparation and proper vacuum cleaning plays a vital role in creating defect-free heavy-duty coating.

From Bonny Njimogu of Construction Specialist Services Ltd. on July 10, 2013:
Good surface preparation has been a key factor that contributes to a flawless finish. However,to prevent or remedy the defects with reference to the above, prime the substrate to eliminate hygroscopic pores which may result to pinholes or air pockets. Ensure thorough mixing using a low speed device. Pour out the  material, spread with a squeegee, and roll perpendicularly and slowly with a spike or porcupine roller to eliminate air bubbles.


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Tagged categories: High solid coatings; Holidays; Paint defects


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