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Issue link: http://coatingspromag.epubxp.com/i/72303
A: Keep in mind that throughout rehabi litation, it is virtual ly impossible not to damage the coating on the existing bars, and frequently on the newly installed ones. The uncoated bars, as with all steels, will have areas that are anodic and cathodic to each other. The main problems are the large differences in potential between the chloride-impregnated concrete and the new concrete for the repair area, which has no such chloride impregnation. The area at the joint between the new concrete and the old concrete is the area of greatest potential difference. Any bare steel—pinhole or otherwise—will suffer the greatest and fastest corrosion at this location. When I first realized this problem, I wondered why any structural concrete repairs with new concrete were not automatically cathodically protected. The cost is so minimal compared to the damage that will occur if the structure does not have cathodic protection. Coating Adhesion Test Vagaries Q: While conducting a recent pull- off adhesion test for a client, the test reached the required adhesion level of 300 psi but popped off within 10 seconds of the required pressure being reached. The coating being tested was an inorganic zinc (IOZ). The client only wanted one dolly applied per area, and in two areas, the same thing happened. One dolly had zinc covering 50% of its area (pulled entirely from the substrate), and the other dolly had 80% of its area covered with the zinc. There were no other requirements or parameters for the test. The area either passed or it failed. Did the coating being tested pass or fail the adhesion test? A: There obviously is a cohesive failure within the zinc, very likely the result of an incomplete cure of the zinc. Was the cure of the zinc tested before the pull test was performed? Remember that most solvent-based zincs need 50 to 80% relative humidity (RH) to cure properly. I would recheck the cure of the IOZ. If epoxy glue will pull the coating apart, one might suspect that an epoxy coating might do the same thing. I would when the going gets tough... we get tougher. Foot traffic, vehicle traffic, heat, cold, the relentless effects of weather... With these kinds of forces stacked against you, it's essential to have a coating that can rise to the challenge - one that you can have confidence in to remain strong and effective no matter how hard you use or abuse it. Wearcoat® clean, non-slip and incredibly tough, Wearcoat® floor coatings define durability. Easy to apply, easy to will give you the edge you need to get the job done - safely and efficiently. Call us today or check us out on the web. Our expert staff is ready to help with any coating needs you have... COATINGS FOR INDUSTRY, INC. Call us today – 215-723-0919 Fax 215-723-0911 www.coatingsforindustry.com Serving the concrete flooring, structural steel, transportation and aerospace industries for over 35 years. Write in Reader Inquiry #1 July 2012 J www.coatingspromag.com 21 be very suspicious of the integrity of the coating and explain why to the customer. A: First, I agree that there may be a curing problem with the IOZ. However, when testing an IOZ with dolly adhesion tests, you are almost always going to get a cohesive failure rather than an adhesive failure because of the high pigment load in this primer. Second, if you were able to reach the minimum specified adhesion by performing the test according to the standard, I would call that a pass. You are not supposed to leave the pulling force on there for any given period. You could discuss if the dolly is pulled off, say one second after you have reached the specified value. But 10 seconds is too long of a period and does not count as being part of the adhesion test performed. If you, as the inspector, COAT SG SERIES ANTI-SLIP COATINGS