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Zinc coating and two pack epoxy worth the price?


MichaelG

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I have had two boats zinc sprayed after shot blasting and finally epoxy coating. But is the zinc spray worth it? I think it represented about a third of the price of the job. I can't think of any downsides other than the cost as the coating is hard and seems to provide a good bond between the epoxy and the steel and is another layer of protection. I suppose the point is what happens when you scrape something are you in worse or better off position? In my experience the zinc coating is quite hard so even if you scrape a rubbing band a layer of zinc is left even when the epoxy is scrapped off. The zinc is also supposed to act as an anode and corrode in preference to the steel if you get a scratch. I think it is worth it, as there are a lot of on costs every time you dock a boat. Blacking is a waste of time as the first bit of diesel that comes floating past will just take it off.

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8 minutes ago, reg said:

Follow the link I gave

I did but I found only bullshit like “it doesn’t skin over therefore it’s not paint”.

 

Im guessing Mr Zinga never encountered paint such as etching primer / zinc chromate etc. Not all paint is like Dulux Emulsion.

Edited by nicknorman
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1 minute ago, nicknorman said:

I did but I found only bullshit like “it doesn’t skin over therefore it’s not paint”.

Then please feel free to refer to it as a paint I'm sure the world will carry on regardless.

 

End of subject as far as I'm concerned.

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2 minutes ago, nicknorman said:

I did but I found only bullshit like “it doesn’t skin over therefore it’s not paint”.

 

I'd say it is not paint judging by the Wikipedia definition of paint.

 

"Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film."

 

https://en.wikipedia.org/wiki/Paint

 

Pigmented (my emphasis) suggests to me a essential function of paint is to apply colour. Zinga does not perform this function. Nor do a number of other products which you "paint on", e.g varnish, Owatrol etc. 

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11 minutes ago, Mike Adams said:

I have had two boats zinc sprayed after shot blasting and finally epoxy coating. But is the zinc spray worth it? I think it represented about a third of the price of the job. I can't think of any downsides other than the cost as the coating is hard and seems to provide a good bond between the epoxy and the steel and is another layer of protection. I suppose the point is what happens when you scrape something are you in worse or better off position? In my experience the zinc coating is quite hard so even if you scrape a rubbing band a layer of zinc is left even when the epoxy is scrapped off. The zinc is also supposed to act as an anode and corrode in preference to the steel if you get a scratch. I think it is worth it, as there are a lot of on costs every time you dock a boat. Blacking is a waste of time as the first bit of diesel that comes floating past will just take it off.

Does it not look a bit odd if you scrape off the blacking to reveal shiny zinc underneath?

5 minutes ago, MtB said:

 

I'd say it is not paint judging by the Wikipedia definition of paint.

 

"Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film."

 

https://en.wikipedia.org/wiki/Paint

 

Pigmented (my emphasis) suggests to me a essential function of paint is to apply colour. Zinga does not perform this function. Nor do a number of other products which you "paint on", e.g varnish, Owatrol etc. 

Note the comma and the or. My reading of it is that pigmented is just one of the possible properties of a paint.
 

Anyway would you say that a primer isn’t a paint? For example white primer has titanium dioxide in it, shiny grey zinga has zinc in it. What’s the difference?

Edited by nicknorman
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There are many different brands of paint. I painted mine with Sigma when it was new and used a Sigma zinc rich primer. That lasted pretty well but it was a coal tar epoxy and therefore discontinued. I put a couple of coats of Jotun on after pressure washing and sanding the thing with an orbital sander (never again!) and from what I can see it is still fine. Can't remember which version of Jotun it was but it was described as surface tolerant and it seems to have stuck OK. I use plain old black bitumastic above the waterline as it doesn't go grey (or pink if you use red Jotun) and it is perfectly ok for that.

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36 minutes ago, dmr said:

 

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. 😀

I am hoping thats the case

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What do people do to touch up epoxy above the waterline from scrapes on rubbing strips mainly? 
 

we have Jotamastic 87- applied last year. Is it a case if buying a relatively huge can of it and just keep touching up? As it changes with UV light over time will that become obvious as a touch up or should we consider painting the Jotun hardtop which I presume doesn’t chalk like Jotamastic does

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11 hours ago, reg said:

.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

 

 

That just sounds like a bit of marketing hype to me. They can say what they want about their product within legal limits. They might say "it's not paint" but since they are not responsible for defining exactly what is or isn't "paint" others may have a different view.

 

It's a bit like a company who say "it's not just engine oil" when in fact it's just engine oil. Marketing BS.

Edited by blackrose
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8 hours ago, Stroudwater1 said:

What do people do to touch up epoxy above the waterline from scrapes on rubbing strips mainly? 
 

we have Jotamastic 87- applied last year. Is it a case if buying a relatively huge can of it and just keep touching up? As it changes with UV light over time will that become obvious as a touch up or should we consider painting the Jotun hardtop which I presume doesn’t chalk like Jotamastic does

We don’t “touch up” because it would look patchy. Doesn’t seem necessary anyway.

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9 hours ago, Stroudwater1 said:

What do people do to touch up epoxy above the waterline from scrapes on rubbing strips mainly? 
 

we have Jotamastic 87- applied last year. Is it a case if buying a relatively huge can of it and just keep touching up? As it changes with UV light over time will that become obvious as a touch up or should we consider painting the Jotun hardtop which I presume doesn’t chalk like Jotamastic does

 

You can touch up scrapes above the waterline by abrading the area to give it a key, dusting it off and applying a coat or two over the area. Pot life of mixed paint is relatively short (depends on grade of hardener) but I found it you keep your mixed paint somewhere cool you can get a second coat on after the minimum overcoating application time to save you mixing up more paint for the second coat. To help extend pot life mix in no more than 10% Jotun thinners 17.

 

If you're just touching up a few scrapes you'll probably end up wasting paint though because you won't use what you've mixed.

 

It will look patchy until the new paint chalks over itself.

Edited by blackrose
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There are two kinds of zinc coating.......arcspray ,which is pure metal to metal,and inorganic zinc,which is zinc powder in zinc ethyl silicate binder.....both need a steel grit blasted to white (Class 1) steel surface,or risk failure ......especially the zinc ethyl silicate will come off in sheets if something isnt right........a common cause of failure is the introduction of chloride ion.....a big risk with garnet abrasive. 

Edited by john.k
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10 hours ago, Stroudwater1 said:

What do people do to touch up epoxy above the waterline from scrapes on rubbing strips mainly? 
 

we have Jotamastic 87- applied last year. Is it a case if buying a relatively huge can of it and just keep touching up? As it changes with UV light over time will that become obvious as a touch up or should we consider painting the Jotun hardtop which I presume doesn’t chalk like Jotamastic does

One can? 

It's not two pack then, I would have liked to have spare in tupperware pots at correct mix

Mine is still glossy black above waterline, and boat was a lot faster than when weed covered

Edited by LadyG
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2 hours ago, LadyG said:

One can? 

It's not two pack then, I would have liked to have spare in tupperware pots at correct mix

Mine is still glossy black above waterline, and boat was a lot faster than when weed covered

 

It is quite possible to decant small quantities of the two parts into jamjars, though can be a bit of a messy job. It is then possibly to accurately mix small quantities when required using either kitchen scales, or "drug dealer"  electronic scales for really small quantities, though a steady hand and careful pouring are required.

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2 hours ago, LadyG said:

One can? 

It's not two pack then, I would have liked to have spare in tupperware pots at correct mix

Mine is still glossy black above waterline, and boat was a lot faster than when weed covered

 

No it wouldn't be one can, it would be one big can and a smaller can of hardener.

 

You can't keep mixed epoxy "at the correct mix" in tupperware pots if that's what you meant because it will cure and harden. Perhaps you meant keeping them separately in the correct quantities?

 

6 minutes ago, dmr said:

 

It is quite possible to decant small quantities of the two parts into jamjars, though can be a bit of a messy job. It is then possibly to accurately mix small quantities when required using either kitchen scales, or "drug dealer"  electronic scales for really small quantities, though a steady hand and careful pouring are required.

 

Some epoxies are mixed by volume rather than by weight. Jotamastic 87 and 90 being a couple of examples. The water potable epoxy I used to paint my water tank was mixed by weight. I guess it depends on the brand.

Edited by blackrose
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29 minutes ago, blackrose said:

 

No it wouldn't be one can, it would be one big can and a smaller can of hardener.

 

You can't keep mixed epoxy "at the correct mix" in tupperware pots if that's what you meant because it will cure and harden. Perhaps you meant keeping them separately in the correct quantities?

 

 

Some epoxies are mixed by volume rather than by weight. Jotamastic 87 and 90 being a couple of examples. The water potable epoxy I used to paint my water tank was mixed by weight. I guess it depends on the brand.

 

Perhaps I should have said that, Jotun mixes by volume but if you do a search you can find the weight ratios on the www, they are surprisingly different (and one web site gets the numbers wrong).

The West system is clever as both parts have the same density.

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On 28/11/2021 at 11:39, john.k said:

Are you allowed to paint the hull in marine antifouling?.....not TBT ,obviously ,but a copper one?

Antifouling coatings cling to copper | Business | Chemistry World

On 28/11/2021 at 13:42, Alan de Enfield said:

 

Yes - there is an anti-foul called 'copper coat' that gives (I think) a 20 year guarantee.

I liked this bit in the link I posted, Real boy racer stuff

 

 

"AkzoNobel, for instance, is throwing its weight behind ultraviolet light-emitting diodes (UV-LED). Integrated in protective coatings, they emit UV light to prevent biofouling on the surface of the boat or vessel. The chemical giant expects to bring a first-generation commercial product based on this technology to the market in 2023."

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I have a couple of drums of the copper stuff....called Interspeed,or summat......I didnt buy it,but I believe its something like 50 quid a litre.....drums are very heavy ,I assume ,each drum is possibly 1/3 copper powder.....the old stuff was TBT ,tri butyl tin......unfortunately it was too effective,and got banned.

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On 27/11/2021 at 20:06, 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.

 

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

I have zinga on mine where its damaged it gets light rust which is easily cleaned and recoated, I suspect 2 pack will allow some corrosion to creep underneath it, like paint or other systems used?

I had to dry dock my boat a year after the zinga was applied the zinga blacking wasn't UV proof so it turned silver! However it still provided protection the collision damage was just a scratch with slight rust and took seconds to clean off, since then I have sort of ignored it but next year its coming out for some cosmetic keelblack 

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4 hours ago, peterboat said:

I have zinga on mine where its damaged it gets light rust which is easily cleaned and recoated, I suspect 2 pack will allow some corrosion to creep underneath it, like paint or other systems used?

This confirms the statement made here

 

"...

If the Zinga layer is sufficiently damaged to expose the base metal below, the steel would form a layer of surface rust but no corrosion would take place beneath it. In other words if the surface discolouration was removed the steel below would not be pitted or eroded. This is called "throw" and enables Zinga to protect bare metal up to 3 - 5mm or so away from where the coating ends...."

 

From

https://zinga-uk.com/zinga/how-zinga-works

 

 

 

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