23 October 2017

Preventing and Eliminating Rust

To paraphrase the famous sailor, Eric Hiscock: "The price of the strength of a steel boat is eternal vigilance against rust."

As part of Petronella's restoration, we are re-bedding much of her deck hardware. The first project was P's main sheet winches, under which rust was beginning to appear. Howdy and his crew removed the winches from their steel pads, and added disks of Starboard, which is a wood-like marine-quality material that doesn't rot. I think it must be some sort of plastic or fiberglass. Anyway, they bedded that down well to the steel, and mounted the winch on top. That will prevent rust from developing under the winch in the future, or for at least a long time.

Winch re-bedded on Starboard pad
Unfortunately, no bedding lasts forever -- something that many boat owners don't seem to realize. Eventually, everything needs to be re-bedded if you don't want water intrusion. That includes fiberglass boats, in particular. Steel boats rust very slowly, but a leak in a fiberglass deck can quickly cause serious and expensive problems. A word to the wise!

The boys decided that P's granny bars needed to be-bedded, as some slight rust-stains were beginning to appear around one of the legs. Since the safety bars were through-bolted to the deck, that meant taking down the ceiling under the deck. They decided to give me that job (to keep me out of the way, I think!)

Petronella's ceiling unscrews quite easily, though it's a bit of jigsaw puzzle to put back up again. I soon had the required panels down, and that's when I spotted some rust developing around the vent hole of one of the Dorade vents.

Granny bars removed.
Dorade vent, above deck
Around vent hole, under deck

Under the vent, some water or moisture gathered around the vent hole, and made some rust. Now, this is slow progress... this spot has probably been rusting for many, many years. There was plenty of steel left, so no need for surgery, but as long as the ceiling was down, it was a good opportunity to stop the rust in it's tracks.

The first step was to remove as much of the surface rust as possible. I did this with a scraper, followed up by a cup brush mounted in my portable drill. That got 95% of the rust off. (A drop cloth plus dust mask and eye protection protected both the boat and me from most of the debris.)

The second step was to hit the rust with one of the many 'rust converters' on the market. These products chemically convert the iron oxide into a material that purportedly acts as a primer. You do not remove the converted rust. You just leave it on and prime over it. Howdy likes a product called Corroseal.

Rust converter
This is what you should see when the rust converter has done its thing -- a black coating, where there used to be rust.

Rust after conversion
Once the rust converter has done it's thing, you can prime right over it. In this case, with four coats of Bar-Rust 235 2-part epoxy primer.

After first coat of Bar-Rust
That's all there is too it. No voodoo or magic potions needed. When we re-bed the granny bars again in 10 years, we'll check to see how it looks.

Next Up: More Rust Prevention Tricks


  1. What your doing is wonderful. The boat is becoming new again and will serve you well for many years to come.

    1. Thanks, George. I’m real excited about how this project is turning out. Learning everything I can from Howdy. He’s demystifying the process for me.


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