Painting or Coating Steel

[D Gobby]

Hi all.
Time to once again seek help from the Forum and all its Wisdom.
I just got thru with cutting out the centerboard for the 15' daysailer I'm working on.
Cut it out of 3/16" steel plate with my jigsaw and a few blades.
Question what is the best way to protect the steel from rust etc. Prime and paint if so any suggestions on brands etc. Coat with epoxy and then paint?
I was thinking just primer and paint but I'm allways open to suggestions.
I tried the search function but didn't come up with any answers.
Thanks
Darrel

[imported_Conrad]

Glassing is certainly one solution, but the real key to any long-lived job is proper preparation of the metal. I'd suggest a complete sanding with 36-80 grit, then clean it with muratic acid, available from Home Depot, etc. to completely remove all rust, oil, etc. This will leave it even cleaner and brighter than sandblasting- in fact, with some steels you can watch it start to rust almost immeadiately as the fresh water rinse dries, since there is absolutely no oil, dust, etc. on the surface to protect it! But dry it as quickly as you can, then coat with a catalyzed two or three part epoxy primer, not boatbuilder's epoxy. Check your local autobody supply store.

Almost any finish can go on top of the epoxy, best applied while the epoxy is still a bit soft/damp, without sanding. True enamels, although slow to reach full strength, and polyurethanes will both work well. If the paint is perfectly adhered to a clean substrate you'll find it can take a surprising amount of abuse without chipping or scratching, but almost nobody does an adequate prep job, so the idea of just painting steel has gained an undesrvedly poor reputation! Done right, as described above, a painted surface will easily outlast the average glass/epoxy job.

[ 03-05-2003, 01:43 AM: Message edited by: Conrad S. ]

[Peter Malcolm Jardine]

What Conrad said. I have used this product as a base coat on classic car resto's and it works well. They have a complete system.

www.por15.com (http://www.por15.com)

[ 03-05-2003, 01:59 AM: Message edited by: Peter Malcolm Jardine ]

[Dale Genther]

I second the vote for POR15 , I have used it a lot with good results.

[mmd]

Hot dip galvanizing followed by coal-tar epoxy paint. I'll bet Dave Flemming will have specific details on brands, procedures. Dave?

[NormMessinger]

Pettet makes a coating called "Trailer Coat". It is a one part, metal colored, paint. If you put the lid back on the can wait a week or two you will destroy the can before the lid comes off again.

I don't know what it is nor how it compares with the high tech solutions described above but I painted hot rolled steel rod, 1/2", without any preperation what so ever and stuck it up on the back porch to hold up bird feeders. This was at least four years ago. There is no sign of rust showing through.

I have no idea how the center plate of Prairie Islander is holding up. I cleaned, etched, undercoated, primed and painted with an epoxy system. I really wonder it is any better than if I had just slapped on Trailer Coat.

[RGM]

Shop around to see what it would cost you to have the plate sand blasted and galvanized, actually "sand swept" would probably be sufficient if it's new steel. Sand sweeping is actually called an SP-7 level of preparation by the Steel Structure painting Council. Anyway, if you talk that language to the blasting outfit they will understand. Hand prepping the steel to an adequate degree is called an SP-11, not as good as the sweep or blast. Then immediately following the surface prep get it galvanized, painted or whatever else you want done. The trick is, that whatever coating/treatment is to be applied you want it applied before your freshly prepped steel developes a "rust bloom". As you can imagine that's going to be detrimental. If it were mine I'ld sand sweep or blast it, then get it galvanized as quickly as possible and call it good. The trick with getting anything galvanized (or painted) is to reverse schedule the whole process. First arrange with the galvanizing outfit what day (or two) they can dip your part(s). You don't want it laying around the shop for awhile. Then you talk to Mr. Sandblaster to schedule the day you need to leave his shop (freshly prepped parts in hand) headed directly to Mr. Galvanizer. That's the best way to minimize rust bloom. Good luck.

[ 03-05-2003, 01:03 PM: Message edited by: RGM ]

[paul oman]

Commercially the normal method would be a zinc primer, epoxy mid coat and LPU (llinear urethane) topcoat. Could be had for under $1 per square foot but not in the small amounts you need.

As an alternative I would use a flexibilized epoxy with an optional moisture cured aluminum filled urethane topcoat. - both pretty cheap in quart or two units.

Cheapest would be epoxy with a topcoat of exterior enamel..... Easiest would be two coats of the moisture cured urethanes......

you can email me directly for specifics.. Good luck

paul oman
p.oman@ix.netcom.com

[D Gobby]

Thanks again for the info. Still have not figured out which way to go yet but after looking at the plans trying to figure out how to fair the fore and aft edges by 1/8" over a 2" length leaving only 1/16" left in the center after fairing both sides. It Dawned on me that the board should be 3/8" not 3/16" So now I'll have to figure how to cut the 3/8" plate and start all over again. Damn shame did such a fine job on the first one. Live and learn dummy.

Darrel