Fresh water tank painting.

[rustydiver]

I've finally managed to get all the screws out off the inspection cover too see inside the the tank in preparation to reseal the inside. First thoughts is it's not as bad as expected. 

There was a few big lumps in there will they scrape out. 

Is it still ok to use bitumen based sealer or have others used different.

 

[dmr]

How deep are those pits?

When I looked into mine is was mostly in very good condition but in a couple of places the coating had perforated and the steel was pitted, in fact this had left amazing little worm cast/curly turd mounds of rust. The pitting was about 1.5mm deep. I have read that there can be some unusual rusting mechanisms at the bottom of water tanks. The best approach is back to bare metal and then paint in epoxy (ggogle reactive resins).

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

[cuthound]

On a previous boat we had a share in we had this water tank painted with this. However we sold our share the next year so I can't comment on its longevity.

http://www.resinstore.com/armourguardpw.html

[Ex Brummie]

Remove the rust to bare metal and treat with Rustoleum or similar. Allow to dry thoroughly, then use a bituminous black paint, not bitumen. I think Black Jack is a name that I recall from a couple of years ago when I did mine. At this time of year, it is best to double or treble the dryingtimes for intermediate coats.

[dmr]

30 minutes ago, Ex Brummie said:

Remove the rust to bare metal and treat with Rustoleum or similar. Allow to dry thoroughly, then use a bituminous black paint, not bitumen. I think Black Jack is a name that I recall from a couple of years ago when I did mine. At this time of year, it is best to double or treble the dryingtimes for intermediate coats.

If you are putting in the effort to back to bare metal, or very close to bare metal then its crazy not to use a good proper epoxy.

Note that the two references to epoxy coatings in  above posts refer to one and the same product. Armorguard is seriously good stuff.

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

[David Mack]

Black bituminous, as you might use on your hull, used to be recommended as suitable for potable water tanks. But I haven't seen that on a tin for some years now. You really want something specifically intended for drinking water.

[Ex Brummie]

Bituminous Black is NOT what you use on your hull, that is just bitumen. I have used one n the past that was made by Evo Stik, and is epoxy based with a bituminous content. These are classified as odourless and tasteless, and until a punitive testing and certification scheme was introduced a few years ago, the products were certified for use in water tanks. The standard has not changed, just the EU regulations.

[Chewbacka]

Did mine last year, it's surprising how cramped and unpleasant the derusting job is as you need a proper mask and ear defenders.  Still an angle grinder with a wire brush is a good start.......

[jenevers]

Or you could consider a cement wash, which would fill any pits and create a very smooth, even finish, especially the base of the tank.

[rustydiver]

2 hours ago, Chewbacka said:

Did mine last year, it's surprising how cramped and unpleasant the derusting job is as you need a proper mask and ear defenders.  Still an angle grinder with a wire brush is a good start.......

Thanks your filling with encouragement. Not to do it. ;-)

[howardang]

2 hours ago, jenevers said:

Or you could consider a cement wash, which would fill any pits and create a very smooth, even finish, especially the base of the tank.

I agree about a cement wash- easy to apply once any scale has been removed. Ideally  it should be re-applied each year.

Howard

[Giant]

The dutch barge crowd largely seem to swear by the cement approach, apparently fine for several years at a time if done right with a few coats.

Sticks to the steel like the proverbial, sets very hard, and protects against corrosion because of its alkilinity.

We currently have one of ours drained out and debating whether to go for cement or epoxy. The prep for epoxy is daunting in that space...

[frangar]

What happens if you say "caress" a lock entrance with a cement wash?? I'm guessing if the steel flexes then the cement will crack allowing water behind it?? 

[jenevers]

7 hours ago, frangar said:

What happens if you say "caress" a lock entrance with a cement wash?? I'm guessing if the steel flexes then the cement will crack allowing water behind it?? 

Are you Timothy West?

[Señor Chris]

I used Armorguard epoxy - excellent stuff. No need to take back to bare steel either, just scrape, brush and Vactan.

[dmr]

9 hours ago, frangar said:

What happens if you say "caress" a lock entrance with a cement wash?? I'm guessing if the steel flexes then the cement will crack allowing water behind it?? 

I think that Reactive Resins claim that the filler in Armourguard is tiny rubber particles such that the set epoxy is slightly flexible for this very reason.

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

[pearley]

10 hours ago, frangar said:

What happens if you say "caress" a lock entrance with a cement wash?? I'm guessing if the steel flexes then the cement will crack allowing water behind it?? 

Epoxy also cracks under these circumstances.

Moored at Longwood today where the boat in front is having her water tank 'painted'. They have taken it back to bare steel and are coating it with 2 pack polyurethane. Guaranteed 10 years. £750.

Our epoxy is 10 years old now but has a small crack where rust is showing through. And it's got nothing better to do with Timothy West. If you cruise all year the wind can be a bit unpredictable and push you against bits of concrete you'ld rather avoid.

 

Edited April 3, 2017 by pearley

[rustydiver]

looks like i may go down the Epoxy route, i see they do a sealer you can apply first.

How big off a pot do you think i will need, i worked out the tank is roughly 240Gallons. 

[Bod]

Do the job in very good weather.  I didn't, it took weeks (most of April 2015) to dry!

Allow the tank to dry, then sweep out with a wire brush, and hoover, before using a grinder in there.  Unless you plan to join the Black & White mistrals.  This I also discovered the hard way.

 

Bod

[Señor Chris]

2 hours ago, rustydiver said:

How big off a pot do you think i will need, i worked out the tank is roughly 240Gallons. 

Depends how many coats you want. I managed to get 2 out of 2.5 litres.

[Chewbacka]

12 hours ago, Bod said:

Do the job in very good weather.  I didn't, it took weeks (most of April 2015) to dry!

Allow the tank to dry, then sweep out with a wire brush, and hoover, before using a grinder in there.  Unless you plan to join the Black & White mistrals.  This I also discovered the hard way.

 

Bod

The canal water temperature needs to be above the dew point of the air or you will get condensation.  Once it is, a blower (I used an old bilge blower and a bit of ducting) to mix the air inside the tank and blow in fresh air should dry the steel.  Mine took a couple of hours.  The ducting helps to get fresh air unto the dead spaces.  I think that being cool in there the cold damp 'heavy' air has no reason to rise up out of the tank, so blowing fresh air in mixes and warms the cold damp air and pushes it out the top.

Edited April 4, 2017 by Chewbacka

[Bod]

4 hours ago, Chewbacka said:

The canal water temperature needs to be above the dew point of the air or you will get condensation.  Once it is, a blower (I used an old bilge blower and a bit of ducting) to mix the air inside the tank and blow in fresh air should dry the steel.  Mine took a couple of hours.  The ducting helps to get fresh air unto the dead spaces.  I think that being cool in there the cold damp 'heavy' air has no reason to rise up out of the tank, so blowing fresh air in mixes and warms the cold damp air and pushes it out the top.

Yes that was the problem, no air flow.

Made worse by having to cover to keep the rain out!

 

Bod