Water Tank Maintenance - Specialist Coatings Ltd

[Llamedos]

I’m hoping to tackle the job of re-coating my water tank this autumn and doing my research into the job came across a company called Specialist Coatings Ltd.
 

They have built their business and reputation re coating and renovating often badly corroded water tanks in a variety of situations across all sorts of industries and now sell their product to boat owners for DIY use. Uniquely it’s a fume free water based epoxy which they claim lasts 15-20 years if applied properly and uniquely it can be used over previous bitumen coated surfaces effectively ‘sealing in’ the bitumen which is what appeals most to me. The only downside is the cost - they quote based on the capacity of each tank it doesn’t come cheap believe me. Nevertheless if it’s as good as they claim I’m very tempted. 
 

Has anyone used this stuff and if so what did you think? Was it straightforward to use? Has it lived up to the claims? There are a couple of case studies on the company’s website from narrowboat owners who are clearly delighted with it. 
 

Here’s a link with details…

 

Specialist Coatings

[blackrose]

So on one hand it will last 20 years if applied properly and on the other it's an epoxy coating which can be painted over bitumen? As long as you realise that painting over bitumen isn't proper application of any epoxy. 

 

There are already water potable epoxies on the market and they can all be painted over bitumen if you're foolish enough to waste your money doing that. But the point is you're still then relying on the bond strength of the bitumen to the tank or Vactan or whatever is beneath and it won't really last much longer than...

 

bitumen!

 

If you want to spend a lot of money on a water potable epoxy then my advice is to get it from a reputable manufacturer like Jotun and follow the TDS to the letter. Unfortunately the main disadvantage of Tankguard DW is that it can only be bought in 15 litre units, so ideally you need to split the purchase with someone else doing their tank at the same time.

Edited July 13 by blackrose

[Llamedos]

@blackrose Thanks I hadn’t come across this product, not sure how I missed it!  I’ve sent a couple of questions to Jotun technical support regarding its use on previously coated bitumen tanks. It’ll be interesting to see what they say. I’ll post their reply when it lands. 

[ditchcrawler]

If the bitumen that you paint over is well adhered to the steel what is going to make it come off, Its not going to get banged about and knocked. The main risk surly must be rust where the paint is not adhered if the over coating you are using it truly impervious to water 

[Tony Brooks]

33 minutes ago, ditchcrawler said:

If the bitumen that you paint over is well adhered to the steel what is going to make it come off, Its not going to get banged about and knocked. The main risk surly must be rust where the paint is not adhered if the over coating you are using it truly impervious to water 

 

Not sure if that is true for an integral tank. Unintentional contact between the sides if the bow and hard bits of lock/bank can give it a fair old whack - as witnessed by the dents on my ex-hire boat in that position.

[Llamedos]

@ditchcrawler Yes that was my thinking. The company wouldn’t make a groundless longevity claim, it wouldn’t make good business sense. They have a good reputation from what I can see. 

[blackrose]

8 hours ago, Llamedos said:

@blackrose Thanks I hadn’t come across this product, not sure how I missed it!  I’ve sent a couple of questions to Jotun technical support regarding its use on previously coated bitumen tanks. It’ll be interesting to see what they say. I’ll post their reply when it lands. 

 

Well I have the TDS in front of me and there's nothing in there about painting over bitumen. Surface preparation includes sections on Abrasive blast cleaning and Hand & power tool cleaning. You can download the technical data sheet here. 

 

https://www.jotun.com/ww-en/industries/products/Tankguard-DW

 

If you ask Jotun about painting over bitumen I strongly suspect their reply will be along the lines that I posted previously. Please let us know what they say.

 

1 hour ago, ditchcrawler said:

If the bitumen that you paint over is well adhered to the steel what is going to make it come off, Its not going to get banged about and knocked.  

 

I'm not a paint chemist but I think it's possible that the adhesive or cohesive bond strength of naptha-based  bitumen paint decreases over time and that rate of decay is likely to be faster than a thermoset epoxy paint. I don't think it's simply external forces like water, oxygen and UV exposure that cause materials to degrade at different rates, it may also inherent properties of the materials themselves.

 

Having said that, if the degradation of well-adhered bitumen was say 8 years and it was compatible with the epoxy painted over it then it might be a workable solution. However, bear in mind that the bitumen you're painting over will probably have been exposed to water and air for several years so it won't be in the best condition to start with. So I still think it's better to get rid of it and prep the steel properly.

Edited July 13 by blackrose

[Llamedos]

@blackrose Yep I’ll let you know what Jotun say once I get a reply. I too had read the Tankguard DW technical data and saw there was no reference to bitumen coatings hence sending them a message. 
 

One thing that I am sure of is that I will not be re coating with Bitumen, it’s now been proven to be carcinogenic and apparently is considerably worse when the coating is new.  

[Llamedos]

@blackrose

 

Just got the reply from Jotun, here it is…

 

Good afternoon unfortunately Tankguard DW is only suitable to be applied directly to abrasive blasted steel, and certainly should not be applied over Bitumen which is a non-compatible coating and is not a suitable coating for small fresh water tanks, requiring airless spray application in a number of coats for the coating to work.

 

So you’re quite correct it’s not suitable for application over previous coatings including bitumen but importantly they don’t recommend it for small water tanks at all, on the basis it needs to be applied by airless spray rather than brush. So no good for a narrowboat water tank in any circumstances it seems. 
 

In contrast the product from Specialist Coatings appears entirely different. In particular it has a special primer included in the pack and the company do market it as a product that can be applied over previous coatings whether on a boat or indeed any other water tank. 
 

So, I go back to my original question, has anyone actually used the product from Specialist Coatings?

 

[cheesegas]

I haven't, but I have used this stuff, Acothane DW. Can be applied by brush or roller - on the case studies page, you can see them applying by roller in a massive tank!

https://www.acothaneuk.com/

 

Only downside is the 30 minute pot time, you need to work very very fast and even then, at the 25 minute mark it starts to thicken up. I stripped my tank back to bare metal with a Tercoo.

[David Mack]

1 hour ago, cheesegas said:

I haven't, but I have used this stuff, Acothane DW. Can be applied by brush or roller - on the case studies page, you can see them applying by roller in a massive tank!

https://www.acothaneuk.com/

 

Only downside is the 30 minute pot time, you need to work very very fast and even then, at the 25 minute mark it starts to thicken up. I stripped my tank back to bare metal with a Tercoo.

How did they ensure that you were a "fully trained applicator"?

 

"We ensure that the Acothane DW product range is confidently specified and applied by fully trained applicators with our comprehensive technical support and assistance."

[cheesegas]

Just now, David Mack said:

How did they ensure that you were a "fully trained applicator"?

 

"We ensure that the Acothane DW product range is confidently specified and applied by fully trained applicators with our comprehensive technical support and assistance."

They didn't. I called them up, explained the application and they told me how much to buy on a reseller's website, they don't sell small quantities directly.

[Mickba]

Have you seen the pics of an integral tank PJ Barber posted on his FB?

 

Yikes, praise be for Stainless. 🙄

[Llamedos]

No I haven’t, but I bet you can see your reflection in it. 🙄😂

 

Stainless does have some drawbacks however, if it comes into contact with ordinary carbon steel in the presence of water you can sometimes get galvanic corrosion. Not in the stainless steel but the other metal. People don’t think about this when they use stainless steel. 

Edited July 17 by Llamedos