Steel treatment under sprayed insulation?

What treatment or coating (if any) should be applied to the inside of a steel hull before applying sprayed foam (PUR or PIR) insulation?

Thanks

 

Zinc Chromate primer or hot Zinc flame spray. Make sure you use the "closed cell" version of the product and you need a really, really, clean surface; think ethanol wash.

 

I've done a few that were blast media followed with direct application of closed cell poly urea. It was blast, heavy acetone clean, apply foam. Know of several that held up well to that for decades. Had one heavy glassed fish holds that had surface broken over the shaft alley from non fish freight. Got water ingress and started to cause issues. Was about 19 and given the task of stripping the existing foam..... where it had cracks and ingress it came up fine. Sides and overhead were brutal labor to strip and it was about 20 year old foam direct to previously blasted steel. Surprised me how good the steel looked under that foam.

A local boat had a big hold project foamed this year, it was blasted then epoxy coated and then foamed.

I'd talk to the foam supplier and ask, guessing they will have a pretty good idea of compatibility.

 

Many thanks gentlemen that's very helpful.
Cheers TT

 

Apply a two-part marine-grade epoxy primer to the inside of the steel hull before spraying foam insulation. It prevents corrosion by sealing the metal and protecting it from moisture trapped behind the foam.

 

This product may work for you.
Macropoxy 646 Fast Cure | Sherwin-Williams https://www.sherwin-williams.com/homeowners/products/macropoxy-646-fast-cure

 

Ill reiterate my earlier points.

Many steel boats in the commercial fishing fleet were poly urea foamed direct to recently blasted steel. Im not sure how many years a solution that is, but its measured in decades if done correctly. Ive owned boats done that way as well as worked on many done that way. My old home port the foam applicator would only do it that way as he had some prior coating methods end poorly.

This winter a friend did a spray that was blast, then 235 epoxy followed with spray foam. The applicator has several boats with the same epoxy and foam formulation with the oldest one being about a decade old. Would suggest that its holding up well at this point.


Called a fried who was in on a fairly big foam fail a bit over 10 years ago. A pair of new boats were built with epoxy coated and then foamed holds, several weeks in to the season and the foam began to come off and separate from the wall. It caused a mess on the boat as segments of foam would come off and plug the fish removal pump. The crew would crawl down Each delivery and remove whatever was easy and then it would migrate farther the next trip. Friend was on the boat and remember how miserable they were fighting the foam peeling monster.

Between seasons they did a rush blast and re foam to bare steel and its been that way for the last decade. He was a bit fuzzy on the details, but they figured either the epoxy was incompatible with the foam or the formulation change to the low emissiom foam had made adherence terrible. Either way its worth contacting the foam applicator and making sure whatever you prep and prime with is compatible. Removing it after the fact is a horrid job.