Blacking over 2 pack epoxy

[Amphibian Man]

Hello folks,

Our boat was 2 pack epoxied back in 2015 ( before we bought it). It is up for blacking now. Can anyone tell us if we just go over the existing 2 pack with ordinary blacking or do we have to get it all 2 pack epoxied again? We are struggling to learn what the process should be.

Thanks for any input,

John

[nicknorman]

There is not a lot of difference in the cost of 2 pack Vs single pack blacking in terms of the actual stuff. What costs extra for 2 pack blacking is the necessary preparation - grit blasting. So if it were me I’d put 2 pack on top of the 2 pack. But you can check the difference in price and decide for yourself. Do you know exactly what was put on the boat in 2015? Might be worth checking for compatibility with whatever you plan to put on top, but most likely it will be fine.
Coal tar epoxy was often used in the early 2010s, it is good stuff. Unfortunately someone in an office (probably in Europe) decided it was a health and safety risk and you can no longer get it. The approved stuff is probably not quite as good, but that seems to be the case with a lot of stuff!

When applying 2 pack over 2 pack, as well as the usual jet wash it needs to be abraded - with an orbital sander etc - to ensure the new stuff gets a good key.

 

One of the arguments in favour of 2 pack over 1 pack bitumen is that the former doesn’t dissolve in oil or diesel lying on top of the cut, whereas the latter does.

Edited July 8, 2023 by nicknorman

[Tracy D'arth]

Why would you ever want to cover a superior 2 pack product designed to last for up to 20 years with a  single pack product that will need replacing every 2 to 3 years?

[David Mack]

If you put bitumen blacking over epoxy you can't later go back to epoxy unless you remove all the bitumen first.

Your 2015 epoxy coating is probably mostly in good order, with just a few areas scraped off where the boat has been in contact with lock walls etc. As the costs of docking are the same either way, I would be minded to first pressure wash the hull to remove dirt, marine growth and any obviously loose coating and rust, abrade the whole hull with a wire cup brush in an angle grinder, getting any damaged or rusty areas back as close to bright steel as you can. Then patch prime one or two coats with 2 pack epoxy primer (e.g. Jotun Penguard HB) on the bare metal areas. Then one or two coats of 2 pack epoxy coating (e.g. Jotun 90) over the primed areas, then one more coat of the same over the whole thing.

Paint using a 4" roller with solvent resistant sleeve (available from Toolstation). Don't bother with a roller tray, just dip the roller in the can/paint kettle. The end of the roller will get into most awkward areas and you shouldn't need to use a brush. At the end of each day throw the used sleeve away and start with a fresh one the next day.

If you clean off the bare areas first you can patch prime those straight away, then go on to abrade the sound areas and that will make the best use of your limited docking time.

Allow 48 hours after painting all the underwater and waterline areas before refloating - you can always prioritise these and if necessary do the upper areas later - even after refloating if really necessary.

Edited July 8, 2023 by David Mack

[dmr]

15 minutes ago, David Mack said:

If you put bitumen blacking over epoxy you can't later go back to epoxy unless you remove all the bitumen first.

Your 2015 epoxy coating is probably mostly in good order, with just a few areas scraped off where the boat has been in contact with lock walls etc. As the costs of docking are the same either way, I would be minded to first pressure wash the hull to remove dirt, marine growth and any obviously loose coating and rust, abrade the whole hull with a wire cup brush in an angle grinder, getting any damaged or rusty areas back as close to bright steel as you can. Then patch prime one or two coats with 2 pack epoxy primer (e.g. Jotun Penguard HB) on the bare metal areas. The one or two coats of 2 pack epoxy coating (e.g. Jotun 90) over the primed areas, then one more coat of the same over the whole thing.

Paint using a 4" roller with solvent resistant sleeve (available from Toolstation). Don't bother with a roller tray, just dip the roller in the can/paint kettle. The end of the roller will get into most awkward areas and you shouldn't need to use a brush. At the end of each day through the used sleeve away and start with a fresh one the next day.

If you clean off the bare areas first you can patch prime those straight away, then go on to abraded the sound areas and that will make the best use of your limited docking time.

Allow 48 hours after painting all the underwater areas before refloating - you can always prioritise these and if necessary do the upper areas later.

 

Interesting, I agree with most of this but use a brush rather than roller. Does the Penguard have any advantage over using Jotun90 direct to steel? The data sheets do not really help, but do saw that Penguard is intended for new steel whilst Joton90 is "surface tolerant"

[Sea Dog]

1 hour ago, Tracy D'arth said:

Why would you ever want to cover a superior 2 pack product designed to last for up to 20 years with a  single pack product that will need replacing every 2 to 3 years?

One reason might be that, whilst it's great shrugging off diesel and is very resilient to the elements, it doesn't always withstand the scrapes a boat that cruises inevitably gets from locks, dodgy Armco, the Shroppie shelf, etc. I found any scrapes above the waterline went chalky white on Jotamastic 90, so cosmetically there can be issues. However, my bows were as good as the day I did them 2 years on, as was the waterline. It was the underwater damage I'd only spotted when in crystal clear water that caused me concern. Once you have (or consider you might have) underwater scrapes and damage to attend to, it still ought to come out, whether for routine blacking or 2 pack examination, repair and recoat. Some, including me, would not be comfortable not looking at the underwater bits for much beyond 3 years, less if there's a possibility of coating damage. That said, if you're content your 2 pack is in good shape, maybe extended periods between haul outs are fine.

 

Marina queen's? Definitely. Lightly used boats? Maybe. 

Well-travelled boats? Maybe not.

 

You pays yer money as they say.  A tin of SML Ballastic Black is a little under half the price (£40+) of Jotamastic 90 (£80+) so it's a bit cheaper for materials (depending on how many coats) and an easier job if you DIY or cheaper job if you pay someone else to do it.

 

Anyway, the above is why I've, rightly or wrongly, recently gone back to blacking after trying 2-pack!   

 

 

[Amphibian Man]

Thanks everyone. Really appreciate your thoughts.

[Amphibian Man]

One other thing.......do we black the base of the hull? Sometimes I see boats in dry dock and they are only 6 inches off the ground. 

[Tracy D'arth]

15 minutes ago, Amphibian Man said:

One other thing.......do we black the base of the hull? Sometimes I see boats in dry dock and they are only 6 inches off the ground. 

Yes, if you can. It never used to be done but in later years severe base plate pitting has become an issue.

[Bargebuilder]

Consider overcoating your existing epoxy coating with Chemco glass flake epoxy. Because of the flakes of glass, it is much harder and so less prone to scrapes and scratches than standard two pack hull paints and far, far tougher than ordinary blacking.

 

Have a look at the RA 500M pdf

 

It's easy to apply with a 9" roller and mine is fully intact after 11 years and looks good for another 10 or 15!

TDS - RA 500M (1).pdf

It is a bit more expensive than the Jotan product though.

 

 

 

[ditchcrawler]

1 hour ago, Amphibian Man said:

One other thing.......do we black the base of the hull? Sometimes I see boats in dry dock and they are only 6 inches off the ground. 

I do

[agg221]

On 08/07/2023 at 13:50, dmr said:

 

Interesting, I agree with most of this but use a brush rather than roller. Does the Penguard have any advantage over using Jotun90 direct to steel? The data sheets do not really help, but do saw that Penguard is intended for new steel whilst Joton90 is "surface tolerant"

The surface tolerant epoxy primers are better if you can't gritblast, and are very good for patching in for that reason. They are often more expensive and in my practical experience they often flow less well so it's harder to get a nice, smooth coat. My current preference is a surface tolerant epoxy on the hull and something which flows out better on the cabin and engine parts. I have the luxury of using up various ends of cans of things at the moment and particularly like Banoh 1500 on blast cleaned engine castings as it is largely self-levelling and hides a multitude of sins when it comes to pitting damage. It is also doing a nice job on bits of cabin.

 

Alec

[LadyG]

On 08/07/2023 at 15:18, Sea Dog said:

One reason might be that, whilst it's great shrugging off diesel and is very resilient to the elements, it doesn't always withstand the scrapes a boat that cruises inevitably gets from locks, dodgy Armco, the Shroppie shelf, etc. I found any scrapes above the waterline went chalky white on Jotamastic 90, so cosmetically there can be issues. However, my bows were as good as the day I did them 2 years on, as was the waterline. It was the underwater damage I'd only spotted when in crystal clear water that caused me concern. Once you have (or consider you might have) underwater scrapes and damage to attend to, it still ought to come out, whether for routine blacking or 2 pack examination, repair and recoat. Some, including me, would not be comfortable not looking at the underwater bits for much beyond 3 years, less if there's a possibility of coating damage. That said, if you're content your 2 pack is in good shape, maybe extended periods between haul outs are fine.

 

Marina queen's? Definitely. Lightly used boats? Maybe. 

Well-travelled boats? Maybe not.

 

You pays yer money as they say.  A tin of SML Ballastic Black is a little under half the price (£40+) of Jotamastic 90 (£80+) so it's a bit cheaper for materials (depending on how many coats) and an easier job if you DIY or cheaper job if you pay someone else to do it.

 

Anyway, the above is why I've, rightly or wrongly, recently gone back to blacking after trying 2-pack!   

 

 

Good grief, I never considered the difference in cost of bitumen v two pack because the extra cost is wiped out by the cost of getting the boat out every five years instead of every two years.

More time is needed for two pack, which has a cost, and may be more difficult to arrange.

[Bargebuilder]

Or, extend the period between inspections even further by using the product that is used on oil rigs, the Forth Bridge, cooling water intakes for nuclear power stations and ships ballast water tanks. Although it is relatively undiscovered in the private boating world, glass flake epoxy is recognised in industry as one of the longest lasting, hardest and most resistant steel coatings available.

 

It is easy to mix and apply by brush or roller, and even after many years, after a simple jet-wash it can be over-coated without further abrasion.

 

It is designed for a service life of at least 25 years and is so hard that if you need to remove it you will need an angle grinder!

 

The boat yards won't suggest using it, because they may never see you again for further coats; why would they?

 

Chemco International have a great technical advisor that will explain everything.

[blackrose]

7 minutes ago, Bargebuilder said:

 

Chemco International have a great technical advisor that will explain everything.

 

Are you sure you don't have shares in Chemco International? You seem to do most of their advertising! 🤣

Is this the particular product you're recommending? I had a look on their website which I found a bit confusing and all the other products in the range are fillers rather than coatings.

 

https://www.chemcoint.com/products/diver-cote-ra-500uw-lv/#key-characteristics

Edited August 10, 2023 by blackrose

[Bargebuilder]

Just now, blackrose said:

 

Are you sure you don't have shares in Chemco International? 🤣

I wish.

 

I discovered the product some 15 years ago when a commercial fishing vessel near to us on the East Coast had it applied. I was so impressed that I applied the primer and top coat to my barge from new and I couldn't be more impressed with how it has out-performed the various other two-packs, blackings, epoxy tars etc. used on boats around me.

 

I used it on the hull, topsides and in the bilge and nowhere has is failed. I used more traditional paints on the decks and cabin and the rust bubbles up on those every few years in places, so I wish I had coated everything in glass flake first.

 

I find it frustrating that boatyards refuse to recommend or even acknowledge the existence of a product that is far better than that which they offer as standard.

 

It is a bit more expensive, but as a proportion of the whole job the difference is tiny.

[dmr]

38 minutes ago, Bargebuilder said:

I wish.

 

I discovered the product some 15 years ago when a commercial fishing vessel near to us on the East Coast had it applied. I was so impressed that I applied the primer and top coat to my barge from new and I couldn't be more impressed with how it has out-performed the various other two-packs, blackings, epoxy tars etc. used on boats around me.

 

I used it on the hull, topsides and in the bilge and nowhere has is failed. I used more traditional paints on the decks and cabin and the rust bubbles up on those every few years in places, so I wish I had coated everything in glass flake first.

 

I find it frustrating that boatyards refuse to recommend or even acknowledge the existence of a product that is far better than that which they offer as standard.

 

It is a bit more expensive, but as a proportion of the whole job the difference is tiny.

You keep advertising this company, if their stuff is really good then it would be great, I'm tempted to get a bit and try it, but I have concerns.

 

This huge international marine coatings company looks to be mostly a small bunch of marketing men operating out of a medium sized unit on an industrial estate in Scotland. There is a retired technical man who maybe got his knowledge when "associated" with another company. They sell almst 40 products so must be buying this stuff in, or at least contracting out their manufacturing. Who is formulating it?

 

How can such a small marketing company match the research and expertise of somebody like Jotun?

 

Its not impossible, Reactive Resins were a one man show and they made some decent stuff, but there are alarm bells, and if something is "too good to be true" then ...........

 

My guess is that this stuff has a significant disadvantage that we are not aware of.

 

Do you use your boat and take it through locks etc? and does this stuff stay on? I believe that glass flakes can make a brittle coating that might fail on impacys when the stell moves a bit???

 

I don't buy your theory that boatyards won't use it because its too good, more likely they are not convinced it will last long term, or its higher cost is not justified by better performance. The last thing a boatyard wants is getting a bad reputation due to an epoxy failing after a couple of years.

[Tracy D'arth]

I too am sceptical.  I know where micaceous iron oxide was used as a coating on hulls that it was so hard that hitting it with a big power washer cracked it off like  popcorn. Its adhesion to the steel was low, its surface tension massive.

[rusty69]

21 minutes ago, dmr said:

Do you use your boat and take it through locks etc? and does this stuff stay on?

I was under the impression he used it on his barge which was mostly moored on coastal waters, so maybe not many locks.

[Bargebuilder]

15 minutes ago, dmr said:

You keep advertising this company, if their stuff is really good then it would be great, I'm tempted to get a bit and try it, but I have concerns.

 

This huge international marine coatings company looks to be mostly a small bunch of marketing men operating out of a medium sized unit on an industrial estate in Scotland. There is a retired technical man who maybe got his knowledge when "associated" with another company. They sell almst 40 products so must be buying this stuff in, or at least contracting out their manufacturing. Who is formulating it?

 

How can such a small marketing company match the research and expertise of somebody like Jotun?

 

Its not impossible, Reactive Resins were a one man show and they made some decent stuff, but there are alarm bells, and if something is "too good to be true" then ...........

 

My guess is that this stuff has a significant disadvantage that we are not aware of.

 

Do you use your boat and take it through locks etc? and does this stuff stay on? I believe that glass flakes can make a brittle coating that might fail on impacys when the stell moves a bit???

 

I don't buy your theory that boatyards won't use it because its too good, more likely they are not convinced it will last long term, or its higher cost is not justified by better performance. The last thing a boatyard wants is getting a bad reputation due to an epoxy failing after a couple of years.

I have no idea where Chemco do their manufacturing, but I have used glass flake myself and seen it used on several other coastal vessels. Thinking back, mine must have been on for 14 or 15 years -where do the years go?-  and still looks good.

 

There is no doubt that if you hit concrete hard enough, any coating will be scratched off, but the hardness of the aligned glass flakes without doubt increases the coatings resistance to abrasion; just try and rub it back with abrasive paper if you need convincing.

 

Look at the commercial applications where it's trusted.

 

You are right, my barge is mainly coastal, with occasional visits inland, but it is in salt water and has a half tide mooring so it scapes the gravelly sea bed twice each day; not a kind environment for hull coatings.

 

Chemco's version of glass flake (it is sold by others too), once cured remains flexible. If after several weeks you return to the roller tray you used, you can peel off a 2 or 3mm thickness and bend it back and forth without it fracturing.

 

Fortunately, Chemco will supply 1litre pots, so you really don't have to take my word for it, try it for yourself and any concerns you have will evaporate.

[Bargebuilder]

5 hours ago, blackrose said:

I had a look on their website which I found a bit confusing

I used the RA 500 range of products, but that was the best part of 15 years ago, so if I were you I'd speak to their technical chap for up to date advice on their current range.

 

The website is designed for the commercial market where the stuff is purchased by the pallet load, not for private individuals who want a few tins, although they are very happy to supply.

I guess that water authorities, BNF, ship builders, BP etc have their own technical experts, so Chemco aim their website at them; just a guess. 

[Tracy D'arth]

I used to clean the bath with Chemco I think. Pink stuff.  But I know that they make grinding paste.

[David Mack]

21 hours ago, LadyG said:

More time is needed for two pack,

Why? Having used both bitumen and 2 pack  (on different boats at different times) I would say the application and drying time is much the same.

And if the 2 pack lives up to its promise, then next time Belfast is out of the water the preparation time should be much less than if I had used bitumen.

[DShK]

https://www.icorr.org/development-glassflake-coatings-service-protection-hot-substrates/

 

There might be something to the glass flake coating!

[Bargebuilder]

19 minutes ago, DShK said:

https://www.icorr.org/development-glassflake-coatings-service-protection-hot-substrates/

 

There might be something to the glass flake coating!

The list of users is truly impressive; huge, demanding companies.

 

The product is well established in the arguably more rigorous marine environment, but yet to get the foothold it deserves in the inland waterway market. It will take a few brave boat owners prepared to make the change and spread the word.