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Zinc coating and two pack epoxy worth the price?


MichaelG

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Hi all, I'm considering having my narrowboat hull zinc coated and two pack epoxied. I understand that you should get ten years out of it before it needs redoing. I'd be interested to hear from anyone who has had it done as to whether it lasts as well as claimed or if ten years is a optimistic.

My boat is 57 feet and 15 years old. I have her blacked biannually. The last time she was out for blacking a year ago I had a hull survey which was positive with just some minor pitting to 0.5mm. The baseplate has never had any protection applied. 

Looking at Debdale Wharfs prices I think I'd be looking at around 5k which isn,t too bad when offset against the cost of biannual blacking over a ten year period. I'd be interested in hearing anyones experiences, positive or otherwise. Many thanks.

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There was a thread on this exact topic just a couple of weeks ago, have a search.

If you use your boat, that is moving rather than a static home, then nothing will last ten years because bits will get scraped off.s  o you will still need to come out of the water to make repairs, maybe every three, possibly four years.

 

Epoxy should be seen as a way to give much better protection rather than as a cost saver (or even a break even)

Note that repairs do not require grit blasting, just local abrading back to bare steel.

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I had Jarrah blasted and epoxied in 2010, at 21 years old. The coating  has lasted well ( except on the rubbing strips and stem post) after doing about 15 weeks  boating every year since  and a pull out for exam and coating repairs every 4 years.  Weed pressure washes off really easily.  The 30 year survey said the blast and epoxy process had completely stopped any pitting activity.

 

I am slightly suspicious of zinc spraying.  It is great if the zinc is not mechanically damaged but a scratch through to the steel produces a long thin anodic area which the zinc, in fresh water, struggles to protect electrolytically, so you get what is in effect a long thin pit.

You do need to be intending to keep the boat for at least 10 years to get the benefits.  There is no price premium for an epoxied boat as far as  I can tell.

 

N

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Had mine done at debdale six and a half years ago, recently lifted to jet wash and the whole thing was still looking virtually as new. On that basis not anticipating another lift out for at least five more years, so well worth it.

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If you can afford the upfront capital costs then I would say it is well worth doing. Long term savings on repeated blackings and also, in my experience, no need for anodes so further savings there.

Had mine out of the water after 6 years and found minimal cosmetic touch up required to the blacking.

I would also argue that it adds value to the boat so even if you don't keep the boat you have still got value from doing it.

 

It is absolutely essential that the Zinga is applied to a correctly prepared surface. 

 

 

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No experience of the zinc thing but we had our boat 2-packed in 2012. We did take it out of the water in 2018 but it wasn’t really necessary - once we’d washed the weed and mud off, you couldn’t see where the waterline was. We did add a coat but it wasn’t really necessary.

 

People say “Oh but you’ll scrape it all off anyway” but these are people who have never tried it. Of course it is true that you will scrape it off the rubbing strakes somewhat, but this doesn’t matter because they are very thick. The most important area is the waterline since this is where water and air meet (and oil and diesel to melt your conventional blacking) and you have to try quite hard to scrape it off there. And even when you do scrape it, it doesn’t come off in chunks or separate slightly leaving a gap between blacking and hull for water to linger and corrosion to develop.

 

The only thing we found was that the black does fade after a while, ours became a rather grey-brown colour. But that probably depends on the exact stuff you use.

 

In summary, absolutely worth it and the only people who will disagree are the people who have never tried it.

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We had our boat blasted and epoxy coated. We took it to a dry dock to get new anodes fitted 4 years later (and other work) The man running the dock pressure washed the hull for us and was so surprised at the excellent condition of the hull that he was inviting other boat owners to have a look. Yes you get minor scrape areas to repair, but the vast majority was pristine. I consider this to be worthwhile given extended inspection periods and greatly reduced hull corrosion.

 

Edited by jonesthenuke
Pesky typo
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Just to add to the chorus, I had my boat grit blasted in 2015 and applied 4 coats of jotamastic 87 epoxy, the first 2 coats were the silvery aluminium version to provide greater abrasion resistance and then just 2 coats of plain 87 black which went grey a few months later. 

 

After nearly 7 years it still looks perfect.

 

I'm also skeptical about zinc painting under epoxy. What's the point exactly? The epoxy is your hard wearing barrier layer. If it does get scraped off then surely so would the zinc. Or is the exposed zinc paint meant to sacrificially corrode? I don't really get it but my biggest concern is that most epoxy paints are designed to bond directly to the steel. If you don't get the zinc bonding perfect or the zinc to steel bond isn't as strong as the epoxy to steel bond would have been, then you've just wasted your time and money epoxying the hull.

 

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3 hours ago, nicknorman said:

 

The only thing we found was that the black does fade after a while, ours became a rather grey-brown colour. But that probably depends on the exact stuff you use.

 

 

"Chalking" of epoxy paint is perfectly normal but it doesn't affect the paint's mechanical or bond strength. Jotun make a paint called Hardtop in various colours which can go over the top of the epoxy and won't fade. I think other manufacturers do their own versions.

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5 hours ago, BEngo said:

 

 

I am slightly suspicious of zinc spraying.  It is great if the zinc is not mechanically damaged but a scratch through to the steel produces a long thin anodic area which the zinc, in fresh water, struggles to protect electrolytically, so you get what is in effect a long thin pit.

 

 

I know it's not magnesium paint but surely being a less noble metal than steel the zinc paint would sacrificially corrode even in fresh water. This is what I don't understand about zinga or any zinc painting.

Just now, ditchcrawler said:

Paint jobs offshore consisted of blasting, 2pk zinc hibuild followed by colour 2pk bright red or yellow for top sides and black for legs

 

So can you explain how the system works for us less enlightened types?

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17 minutes ago, blackrose said:

 

 

So can you explain how the system works for us less enlightened types?

Yes, next time your boat is out of the water, you need to paint it with yellow and red stripes above the water line.

 

I think that's wot he sed anyway.

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30 minutes ago, blackrose said:

 

 

So can you explain how the system works for us less enlightened types?

No idea, I just had to put up with the hassle of a paint crew onboard for a few weeks in the summer with sod all to do if the weather was damp. There was a paint inspector employed to make sure it was all done to speck. 

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42 minutes ago, blackrose said:

 

I know it's not magnesium paint but surely being a less noble metal than steel the zinc paint would sacrificially corrode even in fresh water. This is what I don't understand about zinga or any zinc painting.

 

Zinga isn't paint.

 

 

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7 hours ago, dmr said:

There was a thread on this exact topic just a couple of weeks ago, have a search.

If you use your boat, that is moving rather than a static home, then nothing will last ten years because bits will get scraped off.s  o you will still need to come out of the water to make repairs, maybe every three, possibly four years.

 

Epoxy should be seen as a way to give much better protection rather than as a cost saver (or even a break even)

Note that repairs do not require grit blasting, just local abrading back to bare steel.

I bought a boat Two pack from new, it was fine after 20 years,  not recommended BTW. 

I had it wired brushed after power wash and put on three coats of jota mastic 90, plus 4 huge anodes. I hope it will see me out. 

If boat comes out, I ll give it a good power wash and one coat of same, else it can stay in water

I would not bother if boat is not brand new or exceptional. Because its not economic, I don't think

Edited by LadyG
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9 minutes ago, nicknorman said:

According to the manufacturer, it is.

I think you will find they are at great pains to show that it is not a paint.

 

To quote directly, and using their own emphasis, from their site

 

"

Zinga is a unique form of corrosion protection because it provides both Active and Passive protection in a form that's as easy to apply as a paint...

BUT... Zinga is not a paint!

Zinga is an active zinc performance coating which works in conjunction with the metal beneath where as paints are only passive barriers. Regardless of how thick paints are applied, they remain as barriers. Once they are breached corrosion sets in immediately. Despite this significant difference Zinga is still often mistaken for a paint simply because it's liquid and comes in a tin. But there are other more subtle differences. For example it does not "skin over" in the tin because Zinga has an unlimited pot-life and it doesn't go "tacky" like a paint

 

https://zinga-uk.com/zinga

Edited by reg
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8 minutes ago, reg said:

I think you will find they are at great pains to show that it is not a paint

 

 

I must agree with Nick, they do see to be pushing the fact that it is 'paint' :

 

Galvanization or galvanizing (also spelled galvanisation or galvanising) is the process of applying a thin protective layer of zinc to steel or iron, to prevent rusting. The most common method is hot-dip galvanizing, in which the components are submerged in a bath of molten zinc. Alternatively, a layer of zinc can be applied by brush, roller or spray. This is carried out with a paint called Zinga. Zinga is a cold galvanizing paint that tests show will offer greater protection against rust over hot dip galvanizing. Corrosion of zinc is much slower than steel or iron therefore the life of the metal can be dramatically extended. Due to the alloying of the Zinc to the iron, cathodic protection is achieved. Previously hot-dip galvanized steel can simply be over coated with Zinga but any rust should be removed by mechanical means before application. Galvanized steel resistance to rust corrosion depends largely on the thickness of the protective galvanized zinc coating that is applied, we strongly recommend at least 2 coats of Zinga are applied allowing the paint to dry between coats. Galvanized steel will last in excess of 25 years dependant on factors such as high humidity, above 60% and attack from de-icing salt used on highways.

 

 

Zinga cold galvanizing paint is certified under numerous industry standards:

Edited by Alan de Enfield
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6 minutes ago, LadyG said:

I bought a boat Two pack from new, it was fine after 20 years,  ot recommended BTW. 

I had it wired brushed after power wash and putt on three coats of jota mastic 90, plus 4 huge anodes. 

I would not bother if boat is not brand new or exceptional. 

 

There is a lot of justification for grit blasting and 2 packing an older boat as it almost totally stops any pitting from progressing. This is what I did.

I could argue that there is less justification for doing a brand new boat, most new boats are purchased by people in their 50's and 60's and even with no treatment at all the boat will outlast many of them. 😀

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1 minute ago, Alan de Enfield said:

 

I must agree with Nick :

 

Galvanization or galvanizing (also spelled galvanisation or galvanising) is the process of applying a thin protective layer of zinc to steel or iron, to prevent rusting. The most common method is hot-dip galvanizing, in which the components are submerged in a bath of molten zinc. Alternatively, a layer of zinc can be applied by brush, roller or spray. This is carried out with a paint called Zinga. Zinga is a cold galvanizing paint that tests show will offer greater protection against rust over hot dip galvanizing. Corrosion of zinc is much slower than steel or iron therefore the life of the metal can be dramatically extended. Due to the alloying of the Zinc to the iron, cathodic protection is achieved. Previously hot-dip galvanized steel can simply be over coated with Zinga but any rust should be removed by mechanical means before application. Galvanized steel resistance to rust corrosion depends largely on the thickness of the protective galvanized zinc coating that is applied, we strongly recommend at least 2 coats of Zinga are applied allowing the paint to dry between coats. Galvanized steel will last in excess of 25 years dependant on factors such as high humidity, above 60% and attack from de-icing salt used on highways.

Do you have a source for this?

I suspect it isn't from the Zinga site.

 

Thanks 

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13 minutes ago, Alan de Enfield said:

 

One of Zinga's main distributors "Promain"

Thanks.

I'll give the direct Zinga link again and part of their direct quote

 

https://zinga-uk.com/zinga

 

"BUT... Zinga is not a paint!"

 

End of quote.
 

 

I believe that a number of suppliers refer to it as paint even thought Zinga try to discourage it.

In the real world think it is probably easier to just to refer to it as a paint when dealing with a customer rather than get into an involved discussion on what it actually is. Professionals will probably understand that it isn't a paint. for everyone else as long as the instructions are followed then thinking of it as a paint doesn't really matter.

 

 

 

 

Edited by reg
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10 minutes ago, Alan de Enfield said:

 

One of Zinga's main distributors "Promain"

Anyway, it is only semantics. Do you apply it with a brush and “paint” it on? Yes. Is it a coating? Yes. So it is a paint by all normal considerations except perhaps the manufacturers who want to deny it is a paint in order to make it seem special. Well to be fair it is fairly special, but since you paint it on most people would consider it a paint. It doesn’t really matter what you call it, it is what it does/how it behaves that matters!

3 minutes ago, reg said:

Thanks.

I'll give the direct Zinga link again

https://zinga-uk.com/zinga

 

I believe that a number of suppliers refer to it as paint even thought Zinga try to discourage it.

In the real world think it is probably easier to just to refer to it as a paint when dealing with a customer rather than get into an involved discussion on what it actually is. Professionals will probably understand that it isn't a paint. for everyone else as long as the instructions are followed then thinking of it as a paint doesn't really matter.


in what way isn’t it a paint?

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7 minutes ago, nicknorman said:

in what way isn’t it a paint?

Follow the link I gave

 

Zinga is an active zinc performance coating which works in conjunction with the metal beneath where as paints are only passive barriers.

Edited by reg
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