Rust inhibitor

[NYSail]

Hello all…..

so my beneteau keel has small rust spots every season that need to be addressed. In the past after grinding/sanding, I have been using POR-15 and top it off with petit 2000, however it appears to not be holding up. I have heard many folks use Ospho as an inhibitor. Would love to hear others experiences.

thanks!

 

[dlochner]

I'm currently working on a steel boat with raw steel and older steel with failing paint. The protocol we are using is to:

1. Take steel to bright metal
2. Treat with TotalBoat Rust Primer
3. 2 coats of Total Boat Epoxy primer
4. Finish coat.

It is important to treat the bright metal quickly before any oxidation occurs and let it work over night. The epoxy coatings are necessary to ensure no moisture reaches the metal.

Ospo and the TotalBoat Rust Primer are probably similar products. Both are Phosphoric acid which bonds to the steel preventing rust and providing a suitable surface the primer.

 

[dLj]

Ospo and the TotalBoat Rust Primer are probably similar products. Both are Phosphoric acid which bonds to the steel preventing rust and providing a suitable surface the primer.

Phosphoric acid primers covert iron oxide into iron phosphate which is an inert oxide similar in structure to aluminum oxide which is what protects aluminum alloys. Just a FYI

dj

 

[JBP-PA]

That's a pretty reasonable approach for touch up spots. I do something similar on my cast iron keel and it seems to hold up well.
What do you mean when you say it does not appear to be holding up? That's spots you treated last year reappear? It is flaking off? That would imply poor adherence. After sanding/grinding, are you doing the whole POR-15 three step system: degreasing thoroughly, using their metal prep (which I'm guessing is an acid etch), before POR-15 paint?

 

[NYSail]

That's a pretty reasonable approach for touch up spots. I do something similar on my cast iron keel and it seems to hold up well.
What do you mean when you say it does not appear to be holding up? That's spots you treated last year reappear? It is flaking off? That would imply poor adherence. After sanding/grinding, are you doing the whole POR-15 three step system: degreasing thoroughly, using their metal prep (which I'm guessing is an acid etch), before POR-15 paint?

The spots I am doing are ok, but am getting some reoccurring. Maybe I will focus more on the total 3 part system this year..... woops on my part.

Thanks!

 

[FastOlson]

long ago I watched a friend (and boat yard owner) de-rust an iron keel. After he removed the old rust and ground it all smooth, he applied thickened epoxy to the whole keel.
This involved giving it a final sanding and solvent-cleaning, and then immediately -within minutes - cover it with wet epoxy. And... apply that wet epoxy with a wire brush on a drill motor to really force it into a good wet-bond with the keel surface. He said that was the best way he had found, thru experience, to prep/seal the surface to keep the rust from returning for a very long time.
My take away was that new corrosion forms - invisible (to the naked eye) - within minutes due to humidity.

 

[dLj]

Without getting to in-depth - the majority of the iron oxide forms are a porous oxide. Think open cell sponge. They are hydrophilic and the water that is entrapped in that structure allows the continued oxidation even if sealed from the outside.

The description given above is a method to minimize the creation of oxidation after cleaning. It's success is very dependent upon how well it's done.

The use of phosphoric acid type treatments done post mechanical cleaning is beneficial in several ways. Any oxide missed gets converted into iron phosphate - another oxidation state which is essentially an inert oxidation that is non-porous and has no entrapped water. Hence the surface is "stabilized". It allows the application of epoxy or other coating to be done in a more leisurely manner providing a greater effective application time frame and greater environmental conditions to achieve a successful coating system.

dj

 

[dlochner]

long ago I watched a friend (and boat yard owner) de-rust an iron keel. After he removed the old rust and ground it all smooth, he applied thickened epoxy to the whole keel.
This involved giving it a final sanding and solvent-cleaning, and then immediately -within minutes - cover it with wet epoxy. And... apply that wet epoxy with a wire brush on a drill motor to really force it into a good wet-bond with the keel surface. He said that was the best way he had found, thru experience, to prep/seal the surface to keep the rust from returning for a very long time.
My take away was that new corrosion forms - invisible (to the naked eye) - within minutes due to humidity.

This method works for lead keels. The wire brushing is to increase the surface area on the lead face and to ensure the epoxy is pushed down into the scratches. Lead oxidizes a little slow than iron and is softer than iron, thus it works. I am not certain about how well it works on steel.

 

[TimFromLI]

I have an iron keel:
1. sand blast it with aluminum oxide (while wearing a face mask/respirator)
2. treat it with ospho
3. fill and fare with epoxy.
4. paint with interlux 2000e

I only sand blast if there's a lot to fix - it makes a big mess and is a pain to clean up otherwise grinder/brush. The repair I do lasts a heck of a lot longer than the repairs by the fiberglass guy in our yard.

 

[Urban Hermit]

I've used both. Ospho can't hold a candle to POR15. The comparison is table wine vs. uncut moonshine. I am puzzled, though, why the POR15 isn't working well. It's UV degradable and above water needs to be painted over but that can't be your issue. It is also primarily formulated to convert the molecular structure of rust to a rust-proof coating, so it works better over rust than over bare metal (although it makes a dandy primer). I took a sailboat trailer down to bare metal, let it develop surface rust, and treated it with POR15. Years of dunking it in salt water did it damage only to the springs, which I didn't coat, and up inside the V where I couldn't get a brush.

 

[NYSail]

I've used both. Ospho can't hold a candle to POR15. The comparison is table wine vs. uncut moonshine. I am puzzled, though, why the POR15 isn't working well. It's UV degradable and above water needs to be painted over but that can't be your issue. It is also primarily formulated to convert the molecular structure of rust to a rust-proof coating, so it works better over rust than over bare metal (although it makes a dandy primer). I took a sailboat trailer down to bare metal, let it develop surface rust, and treated it with POR15. Years of dunking it in salt water did it damage only to the springs, which I didn't coat, and up inside the V where I couldn't get a brush.

I think my issue has been the prep. I will try again this spring and use the kit…..