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That Debdale page rang a very distant alarm bell with me. See http://www.vmzinc-us.com/zinc-basics/compatibilities.html

 

I understood that bitumen can have a damaging reaction with Zinc. I suspect a paint on product like Zinga or Galvafroid will have most of the zinc sufficiently barrierd by the dried carrier "paint" but there is no barrier if the hull has been hot galvanised.

 

I don't know enough about the subject to do more than give this pointer but if it were my boat I would not risk a bitumen product and go for epoxy.

 

That site is strange, I know it looks like it is written looking at zinc sheeting but still strange when it states that

 

* "zinc in contact with mild steel is not desirable". Well yes the zinc will sacrificially corrode, that's why we use zinc galvanising. Pretty desirable to me to have a longer life to first maintenance by galvanizing things. Charts available for corrosion rates on the galvanizers association website.

 

* Cement etc is an unacceptable corrosion product. Well mortar or concrete will etch galvanizing a bit when wet but that reaction stops as soon as the concrete or mortar has set.

 

* The bit about bitumen contact is strange. One of the standard construction specifications is to coat with bitumen columns in cavities or where they may get some bimetallic corrosion, that specification has been used to my knowledge for decades without a problem.

 

There are plenty of good references to corrosion control, The Galvanizers Association is very good, the National Physics Laboratory does some good stuff, excellent on bimetallic corrosion and fasteners in timber, there is an encyclopaedia style site on steel set up by the some of the key UK players here http://www.steelconstruction.info/

 

I should add that the Galvanisers Association don't like zinga, they used to recommend Zinga or Metaflux or any of the really high zinc content coatings but I think they got a bit upset by some marketing from Zinga suggesting that Zinga is better than galvanising. Galvafroid has a lower zinc content.

 

Our boat is zinga-ed, it is a great product. The blue bits on the boat are single pack paint, the blacking is 2 pack sprayed on so yes you can put 2 pack on Zinga. Next time we will make sure it has time to harden before we go up the Chesterfield Canal.

 

I have seen molten zinc spray on things too awkward to galvanize, mainly things with asymmetric geometry. Seems to work well, well at least something done in the mid 90s had not rusted last time I saw it. Not sure you could do it on a boat?

 

In response to the query about painting the baseplate here is a photo of ours after 5 years. A bit of surface rust, nothing of any note.r_2011-blacking_20110704_031.jpg

Edited by RichardN
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Our boat is zinga-ed, it is a great product. The blue bits on the boat are single pack paint, the blacking is 2 pack sprayed on so yes you can put 2 pack on Zinga. Next time we will make sure it has time to harden before we go up the Chesterfield.

Thanks Richard, next time my boat needs blacking I will get it done in 2 pack, over the Zinga.

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I too have read that bitumen is not compatible with zinc but I suspect this is based on the common misconception that oil based products generally react with galvanised surfaces.

 

As far as I am aware, and I'll happily give way to someone who has better knowledge of chemistry, zinc does not react in any way with oil/petroleum. This is not to say that something else in an oil based product will not cause a reaction though.

 

I have had direct experience of someone specifying galvanised steel pipes in the fuel system of a standby generator system. The galvaising on the inside of the pipe came away from the mild steel and blocked the fuel filters. Presumably because the diesel fuel interacted with it.

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I have had direct experience of someone specifying galvanised steel pipes in the fuel system of a standby generator system. The galvaising on the inside of the pipe came away from the mild steel and blocked the fuel filters. Presumably because the diesel fuel interacted with it.

I believe there's a school of thought that it's the sulphur in diesel that causes this.

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Could be, it was in the mid 1980's, when I worked for BT and some of their red diesel was very old (large tanks & little running of generators), so oldcdiesel with very high sulphur content (up to 5% IIRC).

 

Anyway resulted in specification change to prohibit any galvanising of fuel system components.

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  • 5 years later...
On 24/11/2014 at 10:38, b0atman said:

I have had my boat done at Debdale In April also had the epoxy finish plus anodes fitted . looks an excellent job .Time will tell .

Only thing is have still not had any Guarantee paperwork when I contacted them in September answer was Mike is still working on it ? there was no mention of any free checks at 5 years .

Hi B0atman,

Im considering having my boat zinc sprayed at Debdale. Just wondering how your hull went on after this process and what it is like 6yrs down the line?

I'd welcome an update from you.

Thanks.

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  • 1 month later...
On 09/07/2020 at 22:52, 247 said:

Hi B0atman,

Im considering having my boat zinc sprayed at Debdale. Just wondering how your hull went on after this process and what it is like 6yrs down the line?

I'd welcome an update from you.

Thanks.

We too. Would it survive the Shroppie shelf or lock scraping?

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On 09/07/2020 at 22:52, 247 said:

Hi B0atman,

Im considering having my boat zinc sprayed at Debdale. Just wondering how your hull went on after this process and what it is like 6yrs down the line?

I'd welcome an update from you.

Thanks.

 

1 hour ago, wandering snail said:

We too. Would it survive the Shroppie shelf or lock scraping?

 

 

I'm not sure you'll get an answer, this is a 6 year old thread, and Boatman has not been on the forum for the last 12 months,

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A lot has happened in my life since I posted on this thread in 2014 (post 20) and I was forced to sell my boat (health of my wife)

The boat was a Colecraft built in 1981 and was cold galvanised, the buyer had a survey and the surveyor said it had the best hull he had ever seen.

Says something about the process. 

Phil

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