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pbozick
Q&A Forum Registered User
Posted: 11/20/2006 1:26 PM
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Polyurea Blisters
We used polyurea as a protective coating on a concrete wastewater treatment tank. We see some blisters / bubbles and are wondering if we should be concerned. Any information on how we might understand or research this matter would be appreciated.
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Sea
Q&A Forum Registered User
Posted: 11/21/2006 4:25 PM
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RE: Polyurea Blisters
Blistering on concrete can happen for several different reasons such as spraying off ratio material, osmotic disbondment, vapor emission, etc. It is important to know what the specific cause is. If it is an isolated incident, you may be okay by just making the necessary repair. However, if it is a problem that may occur throughout the tank, it could lead to major disbonding of the entire coating and therefore complete failure. Did you decontaminate the concrete of salts prior to application of the primer? How soon after application did the blisters appear? Are they all in the same general area or spread out? Above or below the water line?
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Stephen
Q&A Forum Registered User
Posted: 11/30/2006 1:27 AM
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RE: Polyurea Blisters
I am sure the blisters are moisture related. The off ratio scenerio would be OK but I am sure there would be more of an "OH MY GOD" what happend question. The word water around any application is a red flag. If the tank was draind or new, we all know concrete is a sponge and can hold moisture longer than a real sponge. What were the average dew points during the application time? Concrete always looks dry when it is very wet. It is possible the primer did not cure out. I do not know at this time what the cure time of the primer was. Somtimes applicators are so eager to spray they will not let the primer cure out to the manufacturers suggested time. I myself am guilty of that and have had to pay for it. I will always in the future check RH levels within the concrete and follow all of the manufacurers recommendations. After all, they did all the research. Most of them anyway. Are the blisters on the shady or sunny side of the tank?
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RickW
Q&A Forum Registered User
Posted: 4/28/2007 11:00 PM
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RE: Polyurea Blisters
Water or iso spitting / too much iso. Grease from your gun ( first shot of the day). One of your crew steps in a contaminant and then walks on the work surface. Drips of sweat from elbows while wearing Tyveks, Drips of condensation from your respirator. People eating greasy subs/pizza/etc. on surface while you weren't watching. Filler that hasn't totally outgassed. Could be any of the above, I'm sure there's some real good stories about blisters lingering on these boards. I've cut some blisters with an X and glued them down with 3 min. epoxy. I've cut some out and resprayed or filled with batch mix. I've peeled off entire decks and redid them. Try to think about the actual spray day, If it was your first shot of the day and you didn't recirculate material or do a nice long test shot in a bucket it might be a material issue. What did your machine guy see on the pressures? Then think could moisture be the issue. Was the surface/ or fillers totally dry. Nothing outgassing? Then contaminants, grease oils etc. If you break it down you should be able to solve it.
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HAMILTON
Q&A Forum Registered User
Posted: 5/29/2007 6:23 PM
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RE: Polyurea Blisters
Think about temperature, as well. If enviroment temperature is low, hose temperature is an issue when starting spraying. As spraying goes on, hose temperature rises and material heaters ser point is achieved at the very end of the hose. While this dosen't happen, material can go out off-ratio for a while, causing blisters.
I would suggest you, as well, to cut off one of the blisters, and see if the void is between layers of the polyurea. This is a prove for an off-ratio problem.
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Jefferson
Q&A Forum Registered User
Posted: 6/12/2009 3:25 AM
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RE: Polyurea Blisters
Temperature may be the main issue for this blistering as far i understand about it. I don't think you should crack all the coating just bcoz of few blisters. It may change with atmosphere/temperature.
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