Suitable paint for water tender internals

[britannia]

I am in the process of refurbishing a 'Noble' water truck, which has now been internally tanked-out using glass fibre.  Water tight and strong!  Any advice on what paint to use to paint the internal of this glass fibre tank?  I have plenty of red oxide rust proofing paint, so tempted to use.  Thoughts? 

[millman]

When I built my Gemma 0-4-0 I purchased the cast aluminium saddle tank, big mistake as the thing was porous so I coated the inside with fibreglass resin and painted over the resin with paint from Precision Paints. Five years has passed since doing it and no paint has come off, and the tank no longer leaks like a sieve.

[flyingfox]

Greetings, what is it exactly that has been applied to the inside of this tank, is it fiberglassed with cloth and resin, or is it just resin alone, no cloth bonded in with it, or could it be an epoxy coating, with no cloth.
All these materials are difficult to get to attach to a paint, unless they have careful treatment before painting, and you have good access to the surface.
provided the tank is watertight, I would be inclined to leave it unpainted, rather than risk the paint flaking and getting into injector and other water feed pipework.
I tried to paint an epoxy treated surface, and the paint flaked away after about 2 to 3 years.
Regards
Brian B

[stevep]

Apr 23, 2023 15:35:22 GMT flyingfox said:

Greetings, what is it exactly that has been applied to the inside of this tank, is it fiberglassed with cloth and resin, or is it just resin alone, no cloth bonded in with it, or could it be an epoxy coating, with no cloth.
All these materials are difficult to get to attach to a paint, unless they have careful treatment before painting, and you have good access to the surface.
provided the tank is watertight, I would be inclined to leave it unpainted, rather tan risk the paint flaking and getting into injector and other water feed pipework.
I tried to paint an epoxy treated surface, and the paint flaked away after about 2 to 3 years.
Regards
Brian B

Agreed.

[marcf]

Being fibreglass is should need to be painted

[92220]

Apr 23, 2023 14:31:55 GMT britannia said:

I am in the process of refurbishing a 'Noble' water truck, which has now been internally tanked-out using glass fibre.  Water tight and strong!  Any advice on what paint to use to paint the internal of this glass fibre tank?  I have plenty of red oxide rust proofing paint, so tempted to use.  Thoughts? 

Hi. Ordinary paints will not withstand being permanently submerged in water. You can use either a swimming pool lining paint, or the bituminous paint on this website  (Rylard Axalta Water Tank Coating) :-  www.boatpaint.co.uk/acatalog/Rylards_Water_Tank_Coating_.html

Hope that helps.

Bob.

[britannia]

Apr 23, 2023 15:35:22 GMT flyingfox said:

Greetings, what is it exactly that has been applied to the inside of this tank, is it fiberglassed with cloth and resin, or is it just resin alone, no cloth bonded in with it, or could it be an epoxy coating, with no cloth.
All these materials are difficult to get to attach to a paint, unless they have careful treatment before painting, and you have good access to the surface.
provided the tank is watertight, I would be inclined to leave it unpainted, rather than risk the paint flaking and getting into injector and other water feed pipework.
I tried to paint an epoxy treated surface, and the paint flaked away after about 2 to 3 years.
Regards
Brian B

HI,

It is glass fibre cloth coated with resin.  Being an open tank (with the lid off), it is easy to access.  I am about to do a watertight test, but I will be disappointed if it is not watertight.  I just had it in the back of my mind that glass fibre work oxidises and needs painting, although I guess the tank will only contain water when it is in use, so not that onerous.   Happy to be wrong and have no need to paint! 

[Neale]

There are two-part epoxies sold for use on boats. A glass fibre boat is usually built using polyester resins which can be very slightly porous leading to a condition known as osmotic blistering. One solution is to paint with one of these epoxies which are chemically compatible with the polyester resin and adhere very well but are also pretty much waterproof. Available in yacht chandlers but they ain't cheap! There are also yacht paints which are good for polyester resin used above the waterline and are somewhat cheaper.

[92220]

Just a small word of warning about marine paints and varnishes:- Bear in mind that boats are anticipated to be repainted and re-varnished very regularly, and at relatively short time cycles. That means that the paints don't have to have a long life, unlike automotive paints do. Often, UV inhibitor is lower than what is required to provide a long life. Saves money!!! I came across this problem often, in the 30 years I had the paint business. Modellers would use marine paint or varnish and after one or two years, the paint or varnish coating would be in need of replacing as it had either badly discoloured or had also started to lose adhesion because they had used the wrong base coat or primer.

Formulea might have changed over the last few years, since I retired, but I certainly wouldn't risk using marine products on a model because there is no incentive for manufacturers to make the paints long-life. There are specialist paints and coating for most requirements, so it is a case of look for the one you need, and be prepared to pay the higher cost of a longer life coating.

I pulled this off the internet to show this is not just what I think:-


THE LIFESPAN OF BOAT PAINTS
March 2021


Marine vessels need a special type of paint that will provide them with the right type of protection. Protecting the boat, ship, yacht, and other vessels and equipment that meet brackish, freshwater and saltwater means using durable and long-lasting paints.


Taking the cost and the time it takes to paint a marine vessel into consideration, the marine paint or coating should last for several years. However, several factors come into play when it comes to marine paints.

How long do marine paints last?
The owner of any marine vessel expects an exterior marine paint to have excellent protection against corrosion, UV rays, abrasion, as well as retain its high gloss. Likewise, they want long lasting boat paint.

Technically, marine paints and coatings should last between two and four years.

Bob.

[millman]

Maybe I am lucky with my paint not coming off, after a run the residual heat from the boiler dries the tank out and it is stored empty.

[92220]

Hi Millman.

That's good. If the paint/varnish is more time in air, and dried with heat, than under water, it should be fine. Unless a paint is designed to be completely waterproof (very difficult) the water slowly infiltrates the structure of the paint/varnish coating, and over time the paint/varnish will break down. As long as there is more time in air than under water, the water will have time to creep back out and not do any lasting harm.

Bob.

[denis M]

In the past I have used what I know as Black Jack for painting the insides of domestic water tanks after having either sealed gaps with fiber glass or a solution called Petaseal, (or similar) for sealing petrol tanks. I have found that two coats of Black Jack, available from most DIY stores, does the trick.

Denis

[millman]

Thanks Bob, I shall remember not to paint the insides in future, I really regret buying the cast ally tank, it seemed like a good idea at the time but it doesn’t hold anywhere near as much water as a sheet brass one would due to the thickness of the casting, it’s about 8mm, a brass tank would hold easily 40% more water.

[britannia]

Apr 24, 2023 8:20:38 GMT 92220 said:

Apr 23, 2023 14:31:55 GMT britannia said:

I am in the process of refurbishing a 'Noble' water truck, which has now been internally tanked-out using glass fibre.  Water tight and strong!  Any advice on what paint to use to paint the internal of this glass fibre tank?  I have plenty of red oxide rust proofing paint, so tempted to use.  Thoughts? 

Hi. Ordinary paints will not withstand being permanently submerged in water. You can use either a swimming pool lining paint, or the bituminous paint on this website  (Rylard Axalta Water Tank Coating) :-  www.boatpaint.co.uk/acatalog/Rylards_Water_Tank_Coating_.html

Hope that helps.

Bob.

Thanks bob, in the end I have gone for the bituminous paint as you have identified.  Goes on quite easily, second very easy.  Water test on tank next week!

[jon38r80]

Black Jack or bituminous waterproofing paint is ideal as is the bitunminous paint that is/was the only accepted paint for the inside of Potable water tanks (cant remember a trade name) as used for coating the inside of old possibly rusty riveted galvanised water tanks in old houses to reseal them and make them fit for drinking. out of.

[92220]

Here is a bituminous paint for potable water tanks www.boatpaint.co.uk/acatalog/Rylards_Water_Tank_Coating_.html though there are lots of others that would do the job. Just type into Google bituminous paint for potable water tanks UK and a load of other brands will come up.

Hope that helps.

Bob.

[millman]

Well yesterday I bit the bullet and took the saddle tank off of Gemma, it only took a couple of hours and managed to get the top of the tank off without breaking any screws or doing any damage, for those not familiar with the loco it has a flat topped tank, about 8x4 inch piece of 16 gauge brass, I am now half way through removing the Precision Paints GWR coach cream that I so carefully applied to the inside. I would rather do the job now than have problems with paint flaking off later. I have had half an hour of fresh air to clear my lungs so back in with the cellulose thinners to finish the job. Many thanks to everyone for their contributions on this topic.