Ask the Expert Question-and-Answer Archive

by Ron Joseph

October, 2004

Corrosion of Fume Hood

Q. A customer of mine has a problem with a chemical fume hood. It seems the interior (painted surface?) is showing signs of corrosion. The chemicals used in the hood are SO2 and SO3. The hood has been in service about 4 yrs. Knowing the manufacturer of the hood if painting is cheaper than Powder coating he would have painted the interior I suspect with an epoxy. Would a specific powder be more resistant to these chemicals?

Epoxy coatings are excellent for chemical resistance, but so are polyurethanes and vinyls. Offhand I don't know which resin system is the best for strong acid resistance (probably sulfuric acid?). Because corrosion is apparently raising its ugly head, you should also query the surface preparation that was followed by the manufacturer. For ultimate corrosion protection the steel substrate should have received a zinc phosphate (or at least an iron phosphate) pretreatment. The application of a corrosion resistant primer might also be a good idea. Without knowing more about the problem I can't comment further. Issues such as coating film thickness, coating integrity, etc., also play into this.

I hope this helps.

Best wishes,

Ron Joseph