Aluminum Oxide Paint and Grounding Tanks
Date: Fall 2012
The paint formerly used on some storage tanks contained aluminum powder, which reflected heat from the surface of the tanks. Why did experts recommend grounding these tanks and storing only noncombustible material in them?
When transferring flammable liquids between containers, it is standard practice to ground the tanks so that static electricity will not build up and create a spark which could ignite the flammable vapors. If the containers are to be exposed to heat (from the sun or other equipment), storage of flammable liquids is not recommended unless the containers are well insulated.
It is likely that the recommendation is due to static charge problems. We have all experienced the case where we touch a doorknob and experience a shock. This spark is enough to set off a flammable liquid or even cause an explosion under the right conditions (think volatile liquid that produces potentially explosive vapors). A metal can, if insulated from the ground, can build up charge. Where this charge eventually discharges could lead to an ignition spark and a possible explosion. Grounding the conductive container makes certain a charge does not build on the container. I would go further, however, if I had such a concern. I would make sure anyone coming into contact with such a container also wore a grounding strap or touched a ground connection before handling the container. This way, no charges built up on someone’s body leapt to the container causing an explosion or possible fire. Aluminum paint has conductive metal in it, and it can make an otherwise insulative material into a conductive one. Thus, you would expect the same concern here. The precautions you take are commensurate with the danger of the liquid contained.
Kyle Bunch, PhD
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Update: November 2011