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BRAND NEW WATER TANK COATING


Charlotte Grace

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4 hours ago, blackrose said:

 

I'm not sure about "food grade" but there are plenty of potable water paints both bitumen based and epoxy:

 

https://www.international-marine.com/type/potable-water-tank-coatings

 

https://www.jotun.com/zw/en/b2b/paintsandcoatings/products/tankguard-dw.aspx

 

https://www.thompsonsweatherproofing.co.uk/media/1343/j4016-thompsons_bitumen-paint-data-sheets_st2.pdf

 

Also I'm not really sure how you'd get a big rigid plastic tank into an integral tank when a typical access hatch is only about 18" square? Unless you're going to cut the deck out! You could have lots of smaller linked tanks I suppose but you'd lose a lot of the volume and the hoses between might freeze in winter.

 

 

 

Thanks

 

I thought Jotun might do something but failed to spot it last time I looked. My tank is done in the Reactive Resins stuff but now they have (sadly) gone bankrupt I will move to the Jotun when I need re-do it. Will probably do the outside in Jotun too, its currently International but we are due for a patch up this year, just need to check they are compatible.

 

...................Dave

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7 hours ago, Tony Brooks said:

Many thanks Dr B for very informed input on a specialist subject thatw eoften find difficult to get difainative answers.

 

Cheers

Dont believe him Tony, hes a muppet ?

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6 hours ago, blackrose said:

Ok I didn't say it would kill you but I think some of the solvents will remain and taint the water. I've never actually tried it myself, but when I asked Jotun's technical manager he told me not to do it for that reason.

 

Why wouldn't you use a potable water compatible epoxy that's designed for the job rather than one that isn't?

Oh I totally agree. Use a potable water one if you can. I doubt if it will be that much different to the others but may give you a bit more peace of mind. The potable water epoxies in the 80's all used xylene as one of the solvent cocktail along with ethyl benzene....note NOT benzene. Benzene has not been used as a paint solvent since the late 70's as it is very carcnigenic. EB is not as bad. The problem in the UK is that temperatures are not often high enough to allow full cure and 20°C is needed for 24 hrs to at least get the solvent out. Peeps here seem to paint at any temperature and water temps are often down at 10°C or less which means the steel temp may not be at 15°C which is the minimum required to get the cross linking done. I'd like it higher to get the solvent out. The accelerated 'low temp' cure epoxies which claim cure down at 5°C do get the crosslinking done but you dont get the solvent out down at that temperature. I'd only paint with epoxy between June and August in the UK - like they do offshore or in refineries.

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The Armourguard water potable epoxy I used a few years ago didn't seem to contain any volatile solvents. 

 

https://www.boatpaint.co.uk/acatalog/Reactive_Resins_MP.html

 

It's no longer available and I don't know if it's as hard wearing as a standard epoxy? I would have used Jotun Tankguard but I think it was only available in 20 litre orders. 

Edited by blackrose
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thanks so much for your help guys, I've been sifting through and trying to get my head around it all.

NB the boat will still be in the boat shed in which it is being finished, so not on the water, and sheltered in some way though only in a big shed)

 

I'm unable to fully go with the Tankguard for cost reasons, so have searched and got to the following. 

 

Plan 1 is as follows, for next Saturday (set temp to be 14 high, 8 low in the night prob)  

 

firstly, get a little heater and have it in the box where/when poss 

 

1 sand it a little by hand

2 hoover that out 

 

3 paint one coat of Sikagard 62 (5kg should cover around 20m2, the tank is about 14m2)

https://www.promain.co.uk/sika-gard-62-drinking-and-clean-water-storage-steel-protection.html

 

4 Go home and have a bath / work for a week while the boat gets finished and moved to the yard  (would work on it crack any curing paint etc?)

 

5 Come back and paint a second coat around 7-10 days later * 

https://www.promain.co.uk/amfilerating/file/download/file_id/8051/ this says i need to wait BETWEEN 30 hours and 3 DAYS which worries me as next week i can't do that timing. 

 

I know this is not perfect but it's built off of what i can afford money / timewise as i work 6 days a week at the moment and its 50 quid each way to get to the boat itself..

 

PLAN 2 is to wait a few weeks and do it when i can actually be there for longer (a saturday - a monday) when it might be warmer (who knows though), and me and a few v generous friends are going up to do the exterior painting. The process would be the same, but instead of 7-10 days later I can do it in the advised time bracket on the application guidelines 

 

My boatbuilders just advised me to come and paint it asap, basically, so they can close it up for me, hence the feeling that i should rush. 

 

Thank you again

 

C

 

 

 

 

 

 

 

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4 hours ago, Charlotte Grace said:

 

 

3 paint one coat of Sikagard 62 (5kg should cover around 20m2, the tank is about 14m2)

https://www.promain.co.uk/sika-gard-62-drinking-and-clean-water-storage-steel-protection.html

 

 

 

PLAN 2 is to wait a few weeks and do it when i can actually be there for longer (a saturday - a monday) when it might be warmer (who knows though), and me and a few v generous friends are going up to do the exterior painting. The process would be the same, but instead of 7-10 days later I can do it in the advised time bracket on the application guidelines 

 

My boatbuilders just advised me to come and paint it asap, basically, so they can close it up for me, hence the feeling that i should rush. 

 

Thank you again

 

C

 

Are,  you sure that its that big I would have guessed at more like 5m

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12 hours ago, Charlotte Grace said:

this says i need to wait BETWEEN 30 hours and 3 DAYS

Then you must follow those instructions.

 

@Dr Bob explained why in a post some time ago; I think it’s because after 3 days the curing of the first coat means that the second coat won’t adhere. Hopefully he’ll come along and explain why recoating instructions for all paints must be strictly adhered to. 

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8 hours ago, WotEver said:

Then you must follow those instructions.

 

@Dr Bob explained why in a post some time ago; I think it’s because after 3 days the curing of the first coat means that the second coat won’t adhere. Hopefully he’ll come along and explain why recoating instructions for all paints must be strictly adhered to. 

Yep.

If it is left more than the three days then the epoxy will cure too much to take the top coat. You would need to abraid the surface to get the second coat to stick. That's why you just can't paint over old epoxy. It can be done via your option one but it will be hard work to do the extra abrasion step. The temp is also a bit low for my liking....although the heater is a good idea.

Plan 2 is a much better idea. That way you can guarantee the intercoat adhesion. The weather also should be warmer!!!!  

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Ok guys

 

thanks very much for your advice and clarification on why to follow certain procedures, or what is necessary if i have to wait longer between coats.

The boat will be moved to the yard then, it will prob start rusting a little over next four weeks but what can you do, i'll give it a little sand and hope for the best.

Atleast I can do the coats properly, eventually

 

Your job here is done (until i begin again in a few weeks lol)

 

Charlotte x

oh and btw i meant just 14m2 total surface area area not volume - it is pretty big

 

xx

 

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  • 1 month later...

I work in the water tank  and water systems cleaning and sterilising field. There are potable 2 pack products we use to do tanks. In fact we did a narrowboat a couple of weeks ago. It's not cheap by any means. But it's the same stuff we use on large older steel tanks in business premises to refurbish them.

On the point of spores in your plastic tanks. You will get a tainting to it if you over disinfect it. Make sure your levels are spot on. In a 25% sodium hypochlorite solution 500ml is enough to treat 1000litres. You must hold this in a full tank I mean a brimming tank for  1 hour. This is because it takes that time to break down the protective coatings. (Spores if I remember right) in order to kill the bacteria. ) 

Please also note it is illegal to discharge chlorinated water.  Even if its neutralised into the canal. You can use another product which is safe to discharge as it is potable but highly expensive. 

 

Note.. You aren't sterilising it... that would only happen if you put it in an autoclave.

If I can help give me a shout. 

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  • 1 year later...
On 20/04/2019 at 07:50, blackrose said:

The Armourguard water potable epoxy I used a few years ago didn't seem to contain any volatile solvents. 

 

https://www.boatpaint.co.uk/acatalog/Reactive_Resins_MP.html

 

It's no longer available and I don't know if it's as hard wearing as a standard epoxy? I would have used Jotun Tankguard but I think it was only available in 20 litre orders. 

Armourguard products are now back in stock at boatpaint.co.uk ?

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