Coal Tar Expoxy Performance

[andymahadeo]

Hey Guys, I'm new to the forum.

Currently I'm working on a project where they have a floating bridge with pontoons across a salt water river in Guyana. We're currently using CTE to coat the pontoons (Carbon Steel) and are getting about 4-5 years out of it before the corrosion gets really bad again. Can anyone tell me past experiences they had with CTE Lifetimes in a similar environment?

 

[TomDOT]

Um, I would not try to add a zinc rich primer and polyurethane topcoat to the existing system. I don't know of any manufacturer who uses CTE in combination that way.

I see four basic reasonable choices, depending on availability, cost of downtime, et cetera.:

1) CTE, plus a maintenance/touchup cycle after 1-2 years to fix the sloppy edges/corners.

2) CTE for the main coating system, plus some type of UV blocking topcoat. Check with your supplier for a recommended topcoat.

3) High-ratio inorganic zinc silicate primer alone. With a good IOZ and good surface prep, this works quite well.

4) IOZ, epoxy midcoat, urethane topcoat.

IOZ is more application sensitive (ie, you can get away with sloppier surface prep with CTE) and you have to be sure you're getting a good IOZ like the original NASA formulation.

 

[mshimko]

The most important factor, IMO, in coating performance is the quality of the surface preparation and environmental conditions dutin coating application and cure. Perform a high quality surface prep, and you should be able to get 10 - 20 years of service. BUT, just try to convince the folks with the checkbooks that it's worth it to provide a near-white blasted and maintain humidity control.....

 

[andymahadeo]

Hey guys, sorry for the delayed response. I'm settling to recommend the Primer, CTE and Poly Urethane system. I was checking through ISO 12944-5 Table A5. I noticed it had under Primer it had both "primer type" and "binder" i am a bit confused since as far as i know, primers are standalone coatings (then most of the time overlain with another coating) i.e. they do not need to be mixed with any binder.

can someone clarify?

 

[andymahadeo]

Link to table

http://imageshack.us/photo/my-images/51/tablea5.png/

 

[CoryPad]

Any coating, including primers, have multiple components: binder, solvent, pigment, etc. That table shows the binder type, and shows whether the primer is a zinc-rich style or other.

 

[SJones]

Andy - hire a coating consultant as it appears to be out of your comfort zone. If you look at the CTE datasheets you will note that very rarely are topcoats recommended. If you can get hold of ISO 20340 it would be more appropriate to the application in question. You can then request the paint manufacturers to support their recommended systems with the requisite test reports to substantiate their performance claims.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[gr2vessels]

Andy,
Listen to the people on the forum, they want to help you. First, you need someone real professional help for this project, use the help as advised, then spend some time to learn what you still don't know for your own benefit and for working similar jobs. This forum is only indication for what you are suppose to learn, is not a substitute for your experience.