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Old 02-23-2018, 02:59 PM   #1
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Powdercoat or Galvanise?

Hi,

I have a crane which I use to lower the dingy from the flybridge. It folds up and is normally covered.
I noticed last time I used it that it is getting a bit of surface rust so it is now on the list for refinishing. Initially I was going to sand it down and give it a couple of coats of enamel but then I thought of powder coating which led me to adding galvanising as an option.

So..... whatever I do, its purely to protect the steel. The crane is usually hidden underneath a cover so I am not really worried about appearance. All our boating is in salt water so it does need protecting.

Any advice/opinions re the protective qualities of Gal or powder coating would be appreciated
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Old 02-23-2018, 03:24 PM   #2
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(I'm in purchasing for the Big Yellow equipment company and have some experience with painting/powder coating)

In my opinion Powder coating is no better or worse than good liquid paint. Most of my suppliers use it in the US due to EPA regulations with VOC's. If the base metal is properly prepared, powder paint is fine. Faraday cage effect (poor coverage in corners due to electrical attraction...very simple explanation...look it up...lots of physics!) and edge coverage are concerns. Sharp edges don't like to hold powder paint and often that's where rust starts. (This happens to us a lot as Laser cut sheet metal leaves a very sharp edge and needs to be sanded to round the edge.)

If it was mine, I would look for an E-coater that will dip it then top coat it with powder. If not then sand blast it and primer/top coat powder will be good...especially if you can find a shop that paints for OEM's and uses good powders.

Good luck,

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Old 02-23-2018, 04:14 PM   #3
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I am an engineer and worked at a company that makes automotive components. We had an in house epoxy powder coat line that ran 2 shifts and we also sent some parts out for E coating when we had requirements for longer corrosion protection.
I would have to agree with Sidney's assessment (even though engineering and purchasing rarely agree lol).
Be advised that epoxy powder coat while excellent for corrosion prevention lacks UV resistance and the paint will turn flat.
Polyurethane paint has excellent UV protection but is not as good for corrosion.
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Old 02-23-2018, 04:15 PM   #4
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How about using an epoxy enamel paint? Bunnings have this stuff:

White Knight Paints - Epoxy Enamel
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Old 02-23-2018, 05:00 PM   #5
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Does it rain where you are? I actually uncovered my hydraulic winch and left it out in the breeze because the salt was certainly getting to it but I was preventing the rain from washing it off. I would just paint the crane.
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Old 02-23-2018, 05:19 PM   #6
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How about using an epoxy enamel paint? Bunnings have this stuff:

White Knight Paints - Epoxy Enamel
I`ve used that paint. Not sure how single pack epoxy works, but it does, durable and good gloss.
George, what kind of steel is your hoist? St Croix recommends using polish as protection on their ss cranes,probably 304 not 316.
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Old 02-23-2018, 07:45 PM   #7
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Sometimes the simplest solution is the best. A coat of Rustoleum primer, a coat of light grey ( or whatever you prefer ) and you're done in 2 hours and 20 bucks. Plus you can touch it up in the future if you need to if it gets scratched or whatnot.
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Old 02-24-2018, 06:03 AM   #8
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Galvanizing requires dunking in molten zinc , which can reduce the temper in steel.

The best answer so far,

"Sometimes the simplest solution is the best. A coat of Rustoleum primer, a coat of light grey ( or whatever you prefer ) and you're done in 2 hours and 20 bucks. Plus you can touch it up in the future if you need to if it gets scratched or whatnot."
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Old 02-24-2018, 02:49 PM   #9
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Thanks for the suggestions.

The crane is made of mild steel - the PO was a bit of a handy guy with a welder and he made the crane out of an old mobile engine hoist. Sounds a bit agricultural but it works nicely and I modifies it slightly so it folds up neatly.

Maybe the KISS principle is better in this case - Bunnings White Knight epoxy over the recommended primer should do the trick and save a few boat cents .

Thanks again

BTW, Bunnings is our big box hardware chain
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Old 02-24-2018, 04:01 PM   #10
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I hate anything powdercoated in marine environment. I like paint,your choice of product. Easier to touch up and treat.
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Old 02-24-2018, 05:03 PM   #11
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I'd choose hot-dip galvanizing, if a vendor for that process was conveniently located. Galvanizing thickness is significant (threaded fasteners have special tolerances) so beware of any close-tolerance points in the crane's assembly.
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Old 02-24-2018, 05:50 PM   #12
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One idea would be not galvanising, but metalling, that is cover with a spray of molten zinc or aluminum, such as they do in steel hulls. It is a lot easier than finding a big enough galvanising vat, and probably less expensive.
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Old 02-24-2018, 05:55 PM   #13
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How about cold galvanizing, brushed or sprayed. Not sure if you need to go back to bare metal first. Those bottled "rust converters" seem to work too.
White Knight make a grey undercoat. I remember their etch primer was difficult to apply and get smooth, maybe a light sand, not sure that`s allowed, just before overcoating, would be ok.
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Old 02-25-2018, 08:03 AM   #14
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Galvanizing requires dunking in molten zinc , which can reduce the temper in steel. .................
In the boating world, anchors and boat trailers are often galvanized so It would seem the process doesn't affect steel too much.

In the OP's situation, I would be more inclined to go with paint just because of the look and feel of the finished product.
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Old 02-27-2018, 05:58 AM   #15
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"In the boating world, anchors and boat trailers are often galvanized so It would seem the process doesn't affect steel too much."

Indeed but most are commercial products , which are built by folks that use known materials , with known strengths .

A high load item like a winch can be called upon for many tasks , some that may test the metal .

Paint has less unknown downside on working structures , than galvanized on a lump of anchor.
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Old 02-27-2018, 06:05 AM   #16
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Mfg Engineer here. Powder coat is nice and hard but as previously stated there are issues with corners. Chipping and delaminating are a big concern. No touch will look good.

Primer and paint is the KISS solution.
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Old 02-27-2018, 06:24 AM   #17
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I powder coated mine, two years later there is rust poking its ugly head, Now I am going to make it a maintenance item along with everything else. Powder coat is a good start because they blast and make shiny, little maintenance every spring and you will be good.
To answer your question if you want it grey, galvanize.
If you want it white, powder coat
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