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June 6 - June 12, 2011

What is the preferred method to remove 25-year-old coal tar epoxy from a carbon steel tank in order to reline?


Selected Answers

From vikraman govindraj of Rigmetals L.L.C on August 13, 2011:
     Since it's a 25-year-old coal tar, do the preparation in three steps . First, chip and hammer to remove the old rust, then proceed with sweep blasting to open the face of paint, and finally blast with new garnet to achieve the required grade. This will be time consuming but give good results and safe work.

From Philip Gooden of BlastJet on July 7, 2011:
     Definitely, use UHP water jetting (40,000psi). If the surface profile is not sufficient, follow the UHP with a whip blast using garnet.

From Doug DeClerck of MES on June 9, 2011:

     Are we talking about "HOT ENAMEL" or conventional coal tar epoxy like Koppers 300M? If it is Hot Enamel, then it probably was dumped out and mopped on and could be extremely thick (1/4" or more), and it will get quite sticky in hot weather. Best approach is to do the work in cold weather, chip off the material, and then abrasive blast clean.

      If it is a conventional coal tar epoxy and is under 30 mils, then abrasive blast cleaning out of the gates should work. It may take more abrasive than you think, so plan accordingly. If it is a conventional coal tar epoxy and  is thicker than 30 mils, then you will need to approach the work like a Hot Enamel removal. In any case, protect the workers. The dust can be very aggressive, not just breathing, but skin contact also.

From Lee Edelman of Independant on June 8, 2011:
     Abrasive blast or UHP can be the method. Blast media selection is important if abrasive blast is the selected method. If UHP is the method, depending on the thickness of the coal tar, UHP pressures can range from 30,000 PSI to 50,000 PSI in order to get a WJ2 surface condition. A DH unit will help if the process is done during winter months. Proper PPE and confined spaces certs will be required during this process.

From Gary Peterson of Blason Industries on June 8, 2011:
Chip the coal tar away with either air tools or electric. Sand blast the walls, shotblast the floors using steel shot mixed with grit.

From jesse chasteen of schriener construction on June 7, 2011:
     If the coal tar was applied in the state-of-the-art fashion available 25 years ago, the best way is, RUN-AWAY, and don't do it. (Just kidding) Protect your crew and .send them in with air scrapers and pull of as much of the bulk material as possible before you start sandblasting to required specification. The coal tar will range from 20 mils to greater than 200 mils on this, I would bet. Skin protection and air changes are the key to comfort as the removal of this coating has got to be in the top three for miserable.

From Ryan Simpson of Simpson Sandblasting on June 6, 2011:
     Chip the coal tar and abrasive blast to SSPC-SP 10.

From Travis Miller of Corrpro on June 6, 2011:
Use UHP on the surface.

From Ron Lanter of Protec on July 26, 2011:
     Nothing beats abrasive blasting with sand or black beauty. I hate water blasting. What a mess. I personally would never do it. Those guys are more of a man than me.

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Tagged categories: Paint and coatings removal; Surface Preparation; Tank interiors


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