Rust on windlass electric motor

[Hobiehobie]

We have a Maxwell 2200 electric windlass. Working well, just stripped and greased. But the cover on the motor is VERY rusty. To the point where I am afraid it will be perforated if it rusts much further. Two years ago I removed the motor, wire brushed the rust and sprayed with about four coats of Rustoleum Paint but now it is back to flaky rust.

I am in Antigua on lockdown so commercial solutions are not an option. I was thinking of wirebrushing the casing again and then coating with clear West System Epoxy in an attempt to keep any moisture out. Any ideas, thoughts or alternatives?

[s/v Jedi]

Can you takea multimeter and measure resistance between the negative power terminal and the metal housing. Also, post a picture of all the terminals.

I think you may have a galvanic corrosion problem. There should be no conductivity between the metal housing and any of the power terminals incl. the negative terminal.

Then for painting, do not use a wire wheel. A dremel with hard scotchbrite bit or the drum sander is the best tool. Get all corrosion off and next is the choice of primer. You need a good primer. I recommend Awlgrip CF washprimer. If you can’t get that then may be use Ospho or other rust converter, followed by a 2-component epoxy primer like Awlgrip 545, Interlux Protect2000 etc.

After installing the motor again, recheck with the meter. Also, check that you don’t have any bonding wires attached to the windlass, chain stopper, anchor roller or anything that can create a path from the anchor chain to your DC power system. You can measure with one meter probe on the chain and the other over the motor terminals etc.

[coopec43]

A genuine replacement motor cost $A1065 which I reckon is a bit costly.

But why couldn't one of these be fitted at a fraction of the price? Can anyone advise? (I assume being DC they would reverse?)

https://www.alibaba.com/showroom/1200w-dc-motor.html

[Q Xopa]

Originally Posted by s/v Jedi

Can you takea multimeter and measure resistance between the negative power terminal and the metal housing. Also, post a picture of all the terminals.

I think you may have a galvanic corrosion problem. There should be no conductivity between the metal housing and any of the power terminals incl. the negative terminal.

Then for painting, do not use a wire wheel. A dremel with hard scotchbrite bit or the drum sander is the best tool. Get all corrosion off and next is the choice of primer. You need a good primer. I recommend Awlgrip CF washprimer. If you can’t get that then may be use Ospho or other rust converter, followed by a 2-component epoxy primer like Awlgrip 545, Interlux Protect2000 etc.

After installing the motor again, recheck with the meter. Also, check that you don’t have any bonding wires attached to the windlass, chain stopper, anchor roller or anything that can create a path from the anchor chain to your DC power system. You can measure with one meter probe on the chain and the other over the motor terminals etc.

Agreed it looks like a galvanic issue.
I assume the Windlass is not normally 'powered' when not in use. The Negitive power wire should also be disconnected. If you have a Relay a double pole relay, or simply use another relay, or battery switch.

[Hobiehobie]

Thank you for your ideas. I scraped off the paint and rust. Actually once clean it was not as bad as I first thought. No electrical connection between housing and any of the terminals. But I do generally leave the windlass circuit powered up when at anchor, which is pretty much all the time. I do this to allow quick operation if needed but maybe now I will cut the breaker. Terminals all in good shape, see pic.

As I had limited access to coating options (Antigua is closed) I used a wire brush and screwdriver to clean the casing, wiped with acetone and coated with two coats of West System Epoxy, which I had on board.

[Hobiehobie]

See pics of terminals before cleaning and housing with epoxy coating

[s/v Jedi]

Originally Posted by Hobiehobie

Thank you for your ideas. I scraped off the paint and rust. Actually once clean it was not as bad as I first thought. No electrical connection between housing and any of the terminals. But I do generally leave the windlass circuit powered up when at anchor, which is pretty much all the time. I do this to allow quick operation if needed but maybe now I will cut the breaker. Terminals all in good shape, see pic.

As I had limited access to coating options (Antigua is closed) I used a wire brush and screwdriver to clean the casing, wiped with acetone and coated with two coats of West System Epoxy, which I had on board.

Looks good, but the epoxy will deteriorate. A Scotchbrite with plain water scrub of the finish will remove any amine blush and prep it for some spray paint.

Now here is the important bit: your breaker is in the battery positive, so turning that off like some suggest makes no difference. Your motor is good as you confirmed the negative terminal is insulated. Check between anchor chain and negative power lead and between windlass metal and negative power lead. Also, do a visual check for bonding wires. My boat should have been the ultimate done right but there was a bonding wire wreaking havoc so take a real close look. These things can also ruin anchor chain etc.

I have the Maxwell 3500 but think and assume your’s is the same. A real good upgrade would be a Blue Sea Systems ML solenoid in the negative power lead with the remote control switch in an easy to reach location.

[tkeithlu]

Jedi, is the problem with using a wire wheel before painting its leaving too slick a surface for adhesion, or is there some other problem I have not thought of? I've heard the same advice before, but have not known the "why." Given a steel boat, I often face prepping a rusted surface, and a wire wheel is convenient. Would it work to use a wheel and then rough the surface with sand paper or Scotch Brite?

[s/v Jedi]

Originally Posted by tkeithlu

Jedi, is the problem with using a wire wheel before painting its leaving too slick a surface for adhesion, or is there some other problem I have not thought of? I've heard the same advice before, but have not known the "why." Given a steel boat, I often face prepping a rusted surface, and a wire wheel is convenient. Would it work to use a wheel and then rough the surface with sand paper or Scotch Brite?

Exactly. Primer adhesion is much less when using a wire wheel. A needle gun is very good. There’s also miniature grit blasters ($20 range) that work well on small spots.
Sanding also fixes the problem. Increase surface area

[tkeithlu]

Thank you. I've learned something today.

[bharney]

Maxwell recommends coating the motor and other below deck components with lithium grease to protect against corrosion. I use the grease in a spray can, many years and no corrosion.

[roverhi]

Too late now but would have used POR 15 paint. The stuff loves surface rust, is super hard, and easy to apply. Prep is knock off loose rust with a wire brush, spray with their surface prep and paint. Apply 2nd coat while first coat is still tacky. Once dry paint won't stick to it without sanding to give tooth to the surface. Use it on any rusty steel where salt water and other oxidizing agents eat normal paint.

[PLANET EXPRESS]

Try ospho it soaks in turns oxide to phosphate. Then coat it.

[Flatswing]

second vote for Ospho. Brush/scrape/sand off anything loose, spray or wipe on Ospho which chemically converts the oxide and stabilizes the surface, let dry overnight - paint. I have done several pump motors this way and it appears to work well (though only 1 1/2 yr f/u)

[Disailor]

Hobie2: I have had very good results with the following. To remove the rust I use electrolysis: a container large enough to submerge the part / Some washing soda to make the water more conductive (NOT SALT) / A DC power source / a piece of scrap steel.
Dissolve a tablespoon or 2 of washing soda in enough water to cover the part. Connect the negative to the part & the positive to the scrap piece. Leave for 2-3 hours. Remove & check. rinse & wire brush or if it needs more try another hour. Once rinsed & wire brushed, make sure to dry thoroughly. You can now either re- galvanize or coat the part with equal parts of linseed oil & turpentine (not mineral spirits). Out in the sun to dry & when almost dry lay on another coat, repeat. I have mild steel components of my windcharger mount that I have treated this way that have stayed rust free for going on 7 years now. If you want to paint, use a good exterior oil base enamel.

Good overall info

https://www.youtube.com/watch?v=Qi-tK1jwO-k

Method I use

https://www.youtube.com/watch?v=fBaTkJjlwMY