painting mild steel

[gettinthere]

I'm thinking of making a flopper stopper. simple 2 piece steel with a hinge.
Stainless is expensive so how about mild sheet steel and then paint it?
I would use 316 ss for the hardware.
My question is how to best paint mild sheet steel to protect/delay corrosion in salt water?

[David M]

Remove all the loose rust and paint it with multiple layers of an epoxy coating like Interlux 2000 or Interlux 3000. Then try not to chip the epoxy. The only way to stop rust is to seal out the oxygen. Zinc chromate only slows down the inevitable.

You could also have it galvanized. It would not be very expensive to have that done.

[Hiracer]

Use two-part zinc primer epoxy paint.

[cabo_sailor]

We have some local companies that do powder coating. I should imagine that would work. For the DIY, Sears was marketing a small powder coat kit for around $50.

[Weyalan]

Don't do it.
Use. Stainless. Steel.

Two reasons:
Firstly, by the time you buy all the paints and products that you will need for coating up the mild steel it will cost you as much as it would have to use stainless in the first place.
Secondly, if it is a hinge, it will have moving parts. If it has moving parts, you will certainly wear away at your paint coating. Once the paint coating is worn away you will get rust. Once youhave rust you will never get rid of it. The metal on metal contact is going to be in the hinging part and the performance will end up compromised.

Seriously, you will end up regretting not using stainless.

[Hiracer]

Originally Posted by Weyalan

Don't do it.
If it has moving parts, you will certainly wear away at your paint coating.

Man O Man. I'm not familiar with these things.

If there are moving parts, I concure 110%. Paint will not work.

[captjcook]

To Gettingthere,
I am a mechanical engineer. I am professionally reconstructing a 34 foot steel Ketch. I have been using POR15 as a primer, it it a bit tricky for timing between coats and top coat...There is no perfect coating for mild steel, and I would second the galvanize. With a hinge involed as previously stated you are asking for trouble. I find that SST or in engineering speak CRES (corrosion resistant steel) that the price per pound is not that formidable. That said I am curious about a "Flopper Stopper" having a hinge in the first place....I might be wrong ( has happened in the past) but flopper stoppers look a bit like mushroom anchors working on volumetric displacement like birds on a shrimp boat/trawler, anyway I work closely with a fabrication shop, having many things built at the lowest cost, I just don't see stainless especially 304 (may weep a bit) being that expensive. If you provide a sketch, I will give you a reasonable estimate to build or to expect from a fabricator. You are not talking rocket science!

[Jesse]

I made a pair for a friend using UHDP "ultra high density paper" made by Richlite. It's quite heavy and damn near bullet proof and requires no protective coating at all. he used them for 11 years then sold them with the boat. Woodworking tools are all you need and you can drill and tap it for threads too.
Jesse

[gettinthere]

The hinge and hardware will be stainless and bolted to the plate with stainless screws.

I can get a steel plate for about $20 but I've been seeing SS sheet of about 24" X 24" at over $100. Am I seeing bad pricing? This sheet has to be stiff enough to stay flat while flop-stopping. Perhaps 12 gauge?

A bit of rust over a long term isn't a big deal. This isn't anything structural at all.

[captjcook]

ok now I get the hinge part it can fold up on the down stroke. When I go to my I would like to say friend, He has a drop pile (eccess/scrap) I always can find pieces close to the size I need and then shear to size. You may be dealing with a fab shop that would have to order a full sheet to give you your four square feet, it is not uncommon to charge for a full sheet even if the customer needs less, not wrong in my opinion...if they don't use it all the time, they don't suffer a loss for inventory. Sometimes I have to wait til the shop has leftover in the gauge I need, or go to another shop. Ask for the proper size pieces ie: 12 x 12, shearing is a buck to a buck and a half a stroke, let them know an eighth (Whatever) less is ok if you can do that, they may have a piece close. I would get four 12 x 12 x 1/8 11 gauge pieces for less than $60 easy. 16 gauge (1/16) or 14 ga may be cheaper still. rolled stainless is stiff stuff.
Jim

[gettinthere]

Originally Posted by Jesse

I made a pair for a friend using UHDP "ultra high density paper" made by Richlite. It's quite heavy and damn near bullet proof and requires no protective coating at all. he used them for 11 years then sold them with the boat. Woodworking tools are all you need and you can drill and tap it for threads too.
Jesse

Jesse

I tried many search variations on your "UHDP paper" but struck out. Can you give more info? Perhaps a spelling error?

Also, I will need to bend the sheets, does this stuff form or bend?

[Jesse]

You should be able to get all the info available by Googling "Richlite". I'm told there are many uses for the stuff, I've seen it used for transoms on boats with outboards or out drives, counter tops, hatches, fuel docks and high traffic areas. It doesn't seem to wear at all and so far nothing I've found disolves or discolors the surface. But I don't think it's gonna bend worth a hoot, I don't know if heat would help but it's doubtful. But it is the strongest and toughest material I've found that can still be worked with woodworking tools.
Jesse

[roverhi]

I'll second POR 15. The stuff is super hard and really loves to stick to steel as long as it's grease free. I usually leave stuff to be painted out for a couple of days so it gets an even coat of surface rust before painting. Seems to stick better to light rust than bright metal. But then agian it seems to stick to metal, no matter what.

I have found powder coating to be pretty crappy for stuff that gets abuse in a rust intensive environment. Once you get even the smallest nick in the coating, it begins to rust under the coating until the coating begins coming off in large patches. Doesn't seem to be a cure for the problem as it has happened on every piece of powder coated metal that I own/ed.

Aloha
Peter O.

[Wotname]

Don't powder coat it. Powder coating IS porous, much more so than a good quality paint system (but harder). Ask any honest (and knowledgable) powder coater !!

Go SST as suggested for worry free long life or just pick any good paint system if you can live with early cosmetic rusting and a shorter life / more maintenance. I am sure the SST will be cost effective over a longer period.