Coating Steel

[Bob Smalser]

I have a 5/16th inch mild steel centerboard that needs a new coating capable of resisting salt water, and I have little experience with modern materials for the job.

What should I do after cleaning...acid etch? What primer? And what epoxy coating? Or is powdercoat done at the local body shop an option?

Thanks.

[mmd]

Hot-dip galvanizing would be ideal, but facilities to do so are sometimes difficult to find. Coal-tar epoxy is commonly use on commercial boats such as fish-draggers and tugboats for it's abrasion resistance, but it is both expensive and you are not likely to be able to buy a pint. A good base of steel primer paint followed by a couple of coats of two-part epoxy paint followed by seasonal maintenance may be your best bet. Go to the local highway maintenance depot and ask them what coating procedure they use for maintaining local steel bridges - they will have insight into what is available locally as well as practical experience. Who knows - you might be able to scrounge enough left-overs to make your paint job free.

[GordMay]

Clean the steel, then immediately (within 1 hr.) etch with PHOSPHORIC ACID (available as "Ospho" and may others). Overcoat with with a two-part marine EPOXY (such as "WEST System" & others) to a thickness of 10 mils. Coal-Tar Epoxy is not recommended (OMO). You could finish with a two-part Polyurethane paint, for highest aesthetics.

Bob, I called the people who make West System epoxy with a similar question. They have a two part system for cleaning and etching the metal prior to coating with epoxy. I would check with the manufacturer of the epoxy just to be safe. I do know that West does have some additives that change the color of the epoxy if you'd like to eliminate the painting step.

[gonzo]

VC Tar sells tar epoxy in Qt. cans

Thanks gents.

I used Jasco phosphoric acid after grinding and found some Navy surplus epoxy polymid Mare Island Green epoxy primer and flat white epoxy topcoat. 4 gallons total. All for about 75 bucks at Chimicum Surplus who buy up all the recently-expired gov't shipyard paint.

Phosphate, 1 coat primer, 3 coats of topcoat all applied while the previous coat was still soft. The project is curing in a heated shed now where I'll leave it for a week or so as the 60 degrees in the shed isn't ideal for curing.

[Bob Smalser]

Oops..forgot to log on so I can't edit that...anyway the paint is curing just fine.