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Dear all,

 

I'm wanting to educate myself on what type of paint should be used on my integral water tank. I had it painted last year but it only lasted a few months before rust appearred again, and once again the replacement paint rusted through this year. I'm told that as it's a water tank the rust cannot be treated and that bitumastic paint was used that can't be painted over with anything else. What are my options?

 

Thanks,

 

Phil

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When we bought our boat there was rust coming through the pipes in flecks, and when we opened up the tank there were significant patches.

 

When we repainted (vile job) we spent a long time preparing before painting. We scraped and brushed and wire brushed and sanded off all the rust that we inherited. Then we treated with Fertan. Then we painted with three coats of potable bitumen (can't remember the brand I'm afraid, got it from Uxbridge Boat Centre).

 

Importantly, we allowed each coat of bitumen to dry and harden completely before doing the next coat. If i recall correctly, it was at least a week between each coat, during a nice mild dry spring.

 

Five years on we've never seen a fleck of rust come through, or in the water pump filter. Habitually we don't drink the tank water without filtering or boiling, but it's never tasted bad at all.

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We did/do the same, but using Vactan then one coat of potable bitumen (Midland Chandlers). We don't have the time (unfortunately) to do the three coat treatment, but that sounds like the way to go, as our single annual coat allows the odd patch of rust to peep through before we drain out for winter.

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Ours was done from new 7 years ago with 2 pack and is as good as new. Did worry when we had the anodes replaced last month as the choices of location were either where the tank is or further back where it had been spray foamed. Apparently the foam can give off some noxious fumes so they went where the tank is. Needn't have worried as not a mark on the paint. I guess the water kept the temperature down.

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Thanks for all your advice, seems as if the best route is to wait until the end of the year and get a proper job done, probably in the spring for drying times.

 

The other option I wonder about is having a liner made, but my worry with that is that surely it'll trap moisture between itself and the hull thereby storing up issues for later?

 

 

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Its a horrid job and I confess I paid someone else to do it for me,

Took the tank back to bare metal with an angle grinder then four coats of epoxy from "Reactive Resins". Two coats of primer and two coats of special water tank epoxy.

They claim the resin will still stick even if preparation is not 100% bare metal. Looked really good. Will report back in a few years time.

 

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

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Was cleaning some rust spots in front cratch this week and lo and behold found a hatch to water tank .

It was well hidden under paint tried loosening one screw countersunk slot head .

Not a chance of me undoing them.

It looks like another jar for saving money in is required for hatch removal tank clean and re-paint job.

I will have hexagon headed bolts put in when job is done.

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Was cleaning some rust spots in front cratch this week and lo and behold found a hatch to water tank .

It was well hidden under paint tried loosening one screw countersunk slot head .

Not a chance of me undoing them.

It looks like another jar for saving money in is required for hatch removal tank clean and re-paint job.

I will have hexagon headed bolts put in when job is done.

I have the same issue with a flush fitted hatch/cover which I've always thought is really bad design. I intend getting it cut out and replaced with an upstand over which a proper lid can be fitted. Pretty much like the weed hatch access I have on the trad stern, so that there's no chance of surface water penetrating the gap between the cover and deck. I shudder to think what the inside of my tank looks like.

 

As regards lining, for a proper job epoxy has to be the way to go. I'd be inclined to prime it with Owatrol's Corrosion Inhibiting Primer which they claim does not require sanding/blasting back to clean metal.

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20140626_101742_zpsbqzn6z96.jpg

 

This was a water tank I cleaned out last week - this colour was achieved using only a soft brush down the sides whilst the pump was running, later it was scraped down and washed down again.

I second Dekazer and Pearleys ways of doing things.

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20140626_101742_zpsbqzn6z96.jpg

 

This was a water tank I cleaned out last week - this colour was achieved using only a soft brush down the sides whilst the pump was running, later it was scraped down and washed down again.

I second Dekazer and Pearleys ways of doing things.

Blimey at first glance I thought you were in there wearing diving gear was just about to congratulate you on doing a proper job.

 

Ian.

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This was a water tank I cleaned out last week - this colour was achieved using only a soft brush down the sides whilst the pump was running, later it was scraped down and washed down again.

I second Dekazer and Pearleys ways of doing things.

Hah! You get all the good jobs. ;)

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I have the same issue with a flush fitted hatch/cover which I've always thought is really bad design. I intend getting it cut out and replaced with an upstand over which a proper lid can be fitted. Pretty much like the weed hatch access I have on the trad stern, so that there's no chance of surface water penetrating the gap between the cover and deck. I shudder to think what the inside of my tank looks like.

 

As regards lining, for a proper job epoxy has to be the way to go. I'd be inclined to prime it with Owatrol's Corrosion Inhibiting Primer which they claim does not require sanding/blasting back to clean metal.

 

Owatrols CIP does appear to work moderately well over rusty metal, but If using epoxy I think its best to get much closer to bare metal then use an epoxy primer, not sure if epoxy over CIP is the best approach. Have a look at "Reactive Resins"

 

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

Was cleaning some rust spots in front cratch this week and lo and behold found a hatch to water tank .

It was well hidden under paint tried loosening one screw countersunk slot head .

Not a chance of me undoing them.

It looks like another jar for saving money in is required for hatch removal tank clean and re-paint job.

I will have hexagon headed bolts put in when job is done.

 

I thought about using hex head bolts but the existing slot heads came out ok, though with quite a bit of effort, so I re-used those.

Secret is to use stainless screws and ideally of just the right length so nothing protrudes below the welded on bolt.

 

.........Dave

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If using good two part epoxy you shouldn't really need a primer at all. Jotun have confirmed that the stuff I'm going to use on the outside of my boat doesn't require a primer (Jotamastic 87A). However, I'm not sure if any of these two part epoxies are suitable for potable water. Does anyone know?

 

I may have to give Jotun another call.

Edited by blackrose
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