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Rusting of steel after powder coating removal

Good Afternoon,
I wonder if you can help me.
We are a small company subcontracting shotblasting, beadblasting and powder coating removal. We are at present removing powder coating from steel fire extinguishers, a contract which requires the turn round of 800 to 1000 extinguishers per week. We use a purpose made thermostatically controlled oven for this process. The program we use rises through a controlled rise to 350 °C where it dwells for 1/2 hour. It then rises to 380 °C for a further hour and finally rises to 420 degrees for 4 hours before commencing a cool down program. The whole cycle takes around 8 hours. The whole process is controlled so that if the oven temperature rises quicker than it should vapour injections are made to control the temperature.
After the process we shotblast the extinguishers with steel shot to remove the ash.
We are experiencing a problem with the steel extinguishers rusting very rapidly after blasting. The rusting occurs far more quickly than with other steel items which we remove powder paint from. I am wondering whether the problem is that the oven process is releasing salts in the metal.If this is the case should we endeavour to find an alternative program and if so is there an optimum temperature we should take the temperature up to (bearing in mind that we need a certain heat as powder paint turns to ash at 380 degrees C). We have taken our cycle on advice from the oven manufacturer.

Marilyn Rushworth
- Halifax, West Yorkshire, England

Try to use organic solvent as a stripper for powder from the surface without your old method which make bad effects in steel characteristic due to increase the temperature (heat treatment ).

Ali Gomaa
- Cairo, Egypt

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