Removal of Ash After Burn-off

Q. I really enjoyed your article detailing powder coat stripping, but have one question. We currently utilize the burn-off method in order to clean the hangers. The problem is that the ash is not removed by water quenching. My guess is that I am going to have to install a high-pressure wash station to remove the ash. If I must invest in a high-pressure wash station, could this system replace the actual burn off? C.K.

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A. When parts or racks are stripped in a burn-off oven, the process is referred to as controlled pyrolysis. The oven reaches a temperature of around 800°F and the high temperature slowly breaks down the organic film. Oven temperature is controlled to prevent runaway temperature and flames. Higher temperature would destroy the coating faster, but it would also destroy parts and racks.

When the burn-off cycle is complete, the coating has fallen off. The ash left on the rack is primarily titanium dioxide, an inert pigment that does not break down in the heated oven. It should be removed so that it does not go into the washer or get onto parts being processed.

Most operations use a "high-pressure" spray wand to remove the ash. The issue here is what constitutes "high pressure." The pressure wash system you need to remove ash left from burn-off is not nearly high enough to strip powder. A standard pressure wand will be sufficient to clean off the ash, but it would take much higher pressure to blast off powder.

Pressure washing and water blasting are not the same thing, and they require different equipment. The typical pressure of a spray wand system (1,200 and 2,000 psi) will not strip powder coating. A water blast system that will strip powder could be anywhere from 12,000-40,000 psi. Even with the very high pressure of a water-blast system the process is slow because the powder film is so tough.

Get a decent pressure washer and keep the burn-off oven.