Recommended Coating for Steel Shafts in Chlorinated Water?
Recommended Coating for Steel Shafts in Chlorinated Water?
(OP)
Howdy folks,
I have a project at a municipal water filtration plant (I'm one of the public works engineers) - the flocculator facility makes use of submerged steel shafts (4-7/16" dia.). The water is slightly chlorinated, and comes from a reservoir/lake. I'm quite ignorant when it comes to the myriad of coatings which would suit this application - what we are looking for is to minimize/eliminate maintenance on the shafts.
I'm wondering if one of the plasma/powder coating technologies is applicable and cost effective? Thanks for any input!
John
I have a project at a municipal water filtration plant (I'm one of the public works engineers) - the flocculator facility makes use of submerged steel shafts (4-7/16" dia.). The water is slightly chlorinated, and comes from a reservoir/lake. I'm quite ignorant when it comes to the myriad of coatings which would suit this application - what we are looking for is to minimize/eliminate maintenance on the shafts.
I'm wondering if one of the plasma/powder coating technologies is applicable and cost effective? Thanks for any input!
John





RE: Recommended Coating for Steel Shafts in Chlorinated Water?
nick
RE: Recommended Coating for Steel Shafts in Chlorinated Water?
RE: Recommended Coating for Steel Shafts in Chlorinated Water?
In my experience with thermal sprayed metallic coatings in immersion service they can work if they are top-coated or impregnated with a sealer, but typically they are more expensive than a nonmetallic "paint-type" coating.
RE: Recommended Coating for Steel Shafts in Chlorinated Water?
In low abrasion service, there are plenty of options, sandblasting and painting with a high solids epoxy being a cheap and easy method for a plain shaft. But attachment points (couplings, hubs etc.) and complex surfaces like rake tines etc. are a bit trickier. For most coatings, you need to radius any sharp corners to ensure that the coating doesn't thin at the corners.
RE: Recommended Coating for Steel Shafts in Chlorinated Water?
The shafts do rotate slowly, the paddles are FRP, andthe liquid is lake water. The shaft sections are held together by compression couplings. The end of the shaft assembly passes through a wall (with a seal) where it is driven by a gear and chain off a motor.
What is the longevity of the epoxy coatings? I'm hoping to get 15 years or more before having to refurbish.
YLWEA thanks for the NACE references.
RE: Recommended Coating for Steel Shafts in Chlorinated Water?
http://www.farwestcorrosion.com/fwst/anodgalv/timminco01.htm
RE: Recommended Coating for Steel Shafts in Chlorinated Water?
RE: Recommended Coating for Steel Shafts in Chlorinated Water?
Use an epoxy for the top coat. You need a very good one rated for constant wet service. 100% solids marine epoxies are expensive, but work very well.
Don't plan on 15 years. This needs to be inspected every few years. If coating failure in seen it needs to be re-coated asap or the damage will be severe.
Corrosion never sleeps, but it can be slowed down.