What paint for my steel water tanks?

[AndrewB]

Every three years I've coated the inside of my water tanks with a black bitumous paint called simply 'water-tank paint', that is non-poisonous.

Now they are getting a bit rusty and need painting again. But I can't find water-tank paint anywhere, the chandlers who sold it to me in the past deny all knowledge. Anyone know where to source it - or can you suggest an alternative, safe paint to overcoat the existing?

 

[Ships_Cat]

Epoxy paint systems are produced that are approved for food processing applications such as lining potable water tanks. I cannot direct you to any UK producers but the one we used site is http://www.altexcoatings.co.nz/index.htm - look under the Commercial Marine, and Industrial & Offshore topics at Devran 133 and 230 (under epoxies), and E-Line 939, 949, and 959 (under polyurethanes).

This has been raised on this forum before and many said that you cannot use epoxies. That is entirely incorrect but one must use an approved one. On the site linked to above there is a list of the food use approvals and you will see that it is widely used in the meat industry for potable water - any Englishman who has eaten NZ lamb will have had his meat washed in this.

Main difficulty would be that you may have to remove all the previous coating before application. The payoff is that it is long lived so you will not have to recoat every 3 years.

We found our tanks had a very strong taste for a while which the paint manufacturer (and others) said was unusual and we do not know why, but soon went away with flushing.

Regards

John

 

[Anchorite]

Water Tank Black is still on International's list (good chandleries). Surface preparation of an in-situ steel watertank to reach a level where epoxy will stay on (longer than water tank black) must be nearly impossible. Site is www.yachtpaints.com.

 

[Ships_Cat]

Surface preparation of an in-situ steel watertank to reach a level where epoxy will stay on (longer than water tank black) must be nearly impossible.

Are you claiming that the thousands of built in tanks in new small steel vessels are not prepared correctly then?

If there is access to paint the interior properly (ie to coat all surfaces) then there is access for proper preparation. It may be that a badly designed tank does not have access for coating all surfaces but then both preparation AND painting are a problem and one may as well give up.

John

 

[Anchorite]

Chalk and cheese

The problem here is not a NEW vessel: anyone with any experience of gritblasting the interior of a boat to SA3 (or even the cockpit) knows how extremely difficult it is. To suggest doing it on a fitted-out vessel is a non-starter: but (always willing to learn) you have perhaps a different user-compatible method of surface preparation that your epoxy will survive on.

 

[Ships_Cat]

Re: Chalk and cheese

So the tanks shrink with age do they, making it harder to blast inside them when old /forums/images/graemlins/smile.gif.

The fact existing tanks have an existing paint film on them more than the preprime that a new tank may have is irrelevant. I work in the marine industry, I see it done - perhaps people are cleverer where I operate.

In the end, as I said, it may not be possible to blast some tanks properly, but then you are not going to be able to paint them properly either.

John

 

[tugboat]

As a steel-boat owner myself I understand your problem, though my own tanks are not part of the hull. I couldn't see myself letting a blaster loose inside my boat. An alternative to painting the tanks would be to cement wash them which is what merchant vessels did years ago - maybe still do, I don't know. Use ordinary Portland cement, mix with water to a slurry and lash it on with a big brush (perhaps plugging the suction first). After it dries you'll need to flush the tanks a couple of times to clear any loose bits and clear the taste. Maybe install a filter.

 

[Guest]

Various coatings ...

Cement Wash
Rubberised paint as in swimming pools
Food grade epoxy

Water tank black - which is probably rubberised paint ...

 

[riboid]

Re: Various coatings ...

i can recommend a product from leighs paints which I have personal experience with. sometimes can be a nightmare to apply, well first batch was nightmare and got paint rep to get us batch 2.

tanks were fully blasted to sa 2.5 and sa3 . dont know if this is practical but to ensure proper adhesion of first coat and removal of all traces of previous coatings this is only surface preparation technique.

solvent wash, stripe coat and then spray on.

 

[AndrewB]

Thanks guys!

Many thanks for the tips. I've since spoken to Hempel Paints about this problem. The only paint they are allowed to sell as 'potable' is Hempel 3553, an epoxy only sold in industrial quantities. They also agreed that blasting the steel insides of my tanks bare as required might be possible, but is not altogether practical. They suggested a brand of black varnish (strictly on condition that they were not to be held accountable) which I'm looking out for.

Water-tank paint has disappeared from the current International Paints catalogue (UK - they do offer slightly different ranges in different countries). Thanks for the tip about cement wash, that does seem like a good idea which I will try if I have further trouble.

 

[reeac]

Re: Thanks guys!

Iodophors would provide the required sanitising effect but I assumed that the OP wanted to prevent internal corrosion for the sake of the longevity of the tank and also water quality.

 

[ghostlymoron]

In the water industry we used chlorinated rubber but it needs to be WRC approved.