Painting Steel Boat

[Captain Zay]

Hey all!
So I am not new to the cruising lifestyle, but I am new to the steel boat lifestyle. I've recently purchased a 1998 Bruce Roberts 44 Offshore. It was built in a boatyard, but the ex owner built the interior and painted her.
There are a couple rust spots on the inside but the exterior looks in very good shape, but when I hauled her out there were a couple of little rust pocket/bubbles in spots on the bottom paint (she was in freshwater). Do I need to sand the bottom and repaint or can I sand the rust, prime and repaint over? Thanks!
Fair wind and following seas!

[Oceanride007]

I would say only expose the area where the damage is, don't look for extra work. Treatment now thats another topic.

[AKA-None]

Your best bet is clean it with a needle gun and repair the damaged area

[Tillikum]

A small sandblaster would probably be your best bet. A sandblasting attachment for a pressure washer is a cheap option. Short of chemicals, media blasting is your best chance of completely removing all the rust. A needle gun will remove heavy scale and paint, but will also peen the surface which will tend to enclose pockets of rust in their pits, depending of course on how deeply and widely pitted the surface is. Heat the area to drive out all moisture before you repaint it.

[nuku34]

I had a steel “Joshua” ketch (like Bernard Motiessier’s) for 17 years. Steel’s the Deal, but Rust Never Sleeps. Yes, needle gun is ok for really bad rust, but nothing beats sand-blasting. Sanding with sandpaper is a total waste of time unless you are talking about very small spots of surface (no pitting) rust. Forget “rust converters“, they are just expansive acid which you can buy in generic form, but then again, they don’t remove the rust, and it Will Come Back. Forget oil-based paint too if you really want a coating that will last. Epoxy is the only way to go. Generally steel boats rust from the inside, and usually in places that are hard to see and get at. Blistering in the antifouling usually indicates something is happening with the coating underneath it. If the bottom was not sandblasted very clean and proper epoxy coating applied immediately after blasting, then you are likely to get water infiltrating through the antifoul and then through the epoxy coating then hitting the steel and causing the paint to lift off. Yeah, you can go cheap and just live with the rust as long as the plate thickness is 6mm or more, but that’s not my idea of safety.
I personally love metal boats, if done right, they don’t leak, can bounce off reefs.
Good luck

Sundowner sailing off Fiji in the 1990’s