Painting gas locker with jotamastic 87 epoxy

[Marc Pyn]

Hi folks,

Had a survey when buying boat which said gas locker needs painting and recommended jotun 87. Bought 5L and preparing surface by scraping loose rust and then today trying the angle grinder / cup brush with mask / goggles / long sleeves in the hope to better prep.

 

1st question is - am I OK to bring it back to bare metal without any fear of going through the sides or bottom using this grinder & is this required for jotun epoxy? Steel doesn't bend when I stand / slightly bounce where gas bottle is in pic 1 but some areas are not coming off with scraper - pic 2 shows what came up with some of the bigger bits.

 

I'd like to reduce the amount of power tools in here if scrapers and wire brush are enough, though they arent getting back bare metal just loose stuff. Using grinder for a few mins last night created a lot more loose stuff quickly & quite forcefully getting back to metal shown at bottom of pic 3. With pic 4 zoomed out view. I can kneel outside the gas locker to better use the tool but concerned I don't want to put too much pressure on the surface. I'm not sure what's underneath but from other forum posts there will be some lining / space between this locker and the baseplate / hull sides? 

 

I'm not using valcan rust converter which I've seen mentioned on different posts -  just planning on the epoxy tomorrow as session is booked in with my dad who has lot more painting experience but not with epoxy itself. He was told by a decorator at bowls not to use epoxy in such unventilated small areas so the other question is - is it safe for me to be inside the locker and paint wearing a mask as it says on the spec sheet to use in well ventilated area and don't ingest  fumes.

 

We do have 2 tins of hammerite, so if that's as effective and less dangerous then we won't open the epoxy for this job.

 

We also have a fan which we could use and some DIY long handles so potentially could paint from outside but not sure what we have will work and fumes still be coming upwards. 

 

From outside i can point my head sidewards and with a longer handle reach a fair amount to paint 'blind' so to speak, so I'm hoping that, as we are not looking for a good finish, this may be a safer approach to get the first layer on with paintbrushes to enough of a thickness - making a visual check in between each go?

 

And 3rd question is - it OK to hose down the areas when I've finished preparing today to try and flush out more of the dust or is this a bad idea for any reason with some / all areas on floor being back to bare steel. The dust seems endless when I use the dustpan and i could use a sponge with some sugar soap or detergent if thats better? We also have methylated spirit advised by the jotun seller to use in place of white spirit before applying the 1st coat so will be wiping the surface down in morning before painting.

 

Hope that makes sense & many thanks for sharing any insight / experience. 

Also pic of the ppe I have available 

Edited July 8, 2022 by Marc Pyn
More clarity

[David Mack]

You need to get back to bare metal otherwise the epoxy is a waste of time. I have used a flap wheel in an angle grinder, which is better than a wire brush, but it will continue to grind away steel after you have got through the rust, so use with care.

Hopefully you won't go all the way through, but if you do it indicates that more extensive welded repairs are needed.

The sides of the gas locker are the hull side plates. The space below the gas locker is either an integral steel water tank, or an empty space in which a plastic or stainless steel water tank is located. If its an integral tank you will have an access hatch in the well deck floor, if it houses a separate tank it's a pretty well inaccessible (and unmaintainable) space.

Use a vacuum cleaner to suck out all the rust and dust. Much easier and more effective than a dustpan and brush.

There should be drain holes in th locker to allow any escaped gas to flow out, but I can't see them in the photos. Are they there?

[dmr]

Your doing ok. In the absense of a needle gun that angle grinder/wire cup brush is the way to go. You are very unlikely to go right through but if you do then at least you will know that you have a problem. The bit you have taken to almost bare metal looks ok, you need to push on and do the whole lot.  You have some sheets of rust and getting these off with a scraper is essential, ot might even need an ild screwdriver or hammer and cold chissel. Sometimes the sheets of rust can look like sound metal and be well stuck on, but you need to get them off.  Once the sheets are off then do the whole lot with the wire cup brush. Puuting on epoxy directly without using a rust converter is a very good idea. Epoxy is MUCH better than Hammerite, like much much much better.

Cross posts but same advice, and clean and degrease with Acetone before you put the epoxy on.

[Chewbacka]

43 minutes ago, dmr said:

……………………………… clean and degrease with Acetone before you put the epoxy on.

I personally would not use acetone in a poorly ventilated enclosed space.  The fumes could incapacitate you, it’s highly flammable and at the right mix of vapour to air can explode with a small spark.

Edited July 8, 2022 by Chewbacka

[BEngo]

Get all the rust off.  It will only continue under the epoxy if you don't.   If you are having difficulty with thick sheets of rust, give it a good pounding with a chipping hammer.  Use the chisel end, keeping it reasonably sharp, and go over it one way then again at right angles.  It is like using a needle gun, but harder work.  Then wire brush.

 

After chipping , as well as a cup brush, you will find the slightly coned twist knot type very useful.  It is better for going at corners, and  thick rust.  Usually you can attack from more directions too.

 

Remember to keep the cooling air slots in the grinder clean, or the magic smoke will escape.  A can of air duster is handy for this.

 

Acetone in a confined space can kill you. It is the same as glue sniffing  but with a steel box instead of a crisps packet.  Even meths is likely to have you as high as a kite.

 

N

 

 

[Marc Pyn]

1 hour ago, David Mack said:

The sides of the gas locker are the hull side plates. The space below the gas locker is either an integral steel water tank, or an empty space in which a plastic or stainless steel water tank is located. If its an integral tank you will have an access hatch in the well deck floor, if it houses a separate tank it's a pretty well inaccessible (and unmaintainable) space.

Use a vacuum cleaner to suck out all the rust and dust. Much easier and more effective than a dustpan and brush.

There should be drain holes in th locker to allow any escaped gas to flow out, but I can't see them in the photos. Are they there?

Thanks David, there's drainage holes in the 2 corners. And the stainless steel water tank is under the well deck so doesn't sit under the gas locker like our last did and starts after the cratch board on the bow.

[Marc Pyn]

Thanks Dmr, Chewbacca & Bengo - I'll continue the rest of the afternoon getting back to metal and unless there's any reason not too will use the meths for preparation tomorrow.

 

One thing to double check with all is - is this epoxy 87 safe to be inside the locker - crouched down - regarding its toxicity of fumes - with the pictured mask? And is it OK to paint blind from outsidse so to speak as long as we get a decent thickness on the first coat (then roller the 2nd 24 hours later)

 

Much appreciated all

[blackrose]

1 hour ago, dmr said:

 

... degrease with Acetone before you put the epoxy on.

 

I'd prep and paint up the sides by a couple of inches of I were you.

 

Vacuum out the area after getting it all back to bare steel. If you're going to spirit wipe before painting then use Jotun thinners 17 which is the recommended thinners for Jotamastic 87. Note: the fumes from the thinners are pretty bad in a confined space. 

 

I usually thin the first coat of the Jotamastic with no more than 10% thinners to make sure it gets into all the pits but that's not imperative, just stipple the first coat in well with the brush. If you do thin the paint with thinners 17 then do it after mixing paint and hardener, not at the same time.

 

Pay attention to the mixing ratios and overcoating times given in the technical data sheet for the paint. Are you using standard or winter grade hardener? 

 

I put 3 coats of Jotamastic 87 on my gas locker floor. No problems with fumes. I put a large rubber scraper mat with holes down onto the floor after the paint had fully cured to protect the paint from scraping gas bottles. My gas locker regularly gets flooded as the vents are only a few inches above the waterline, but now it's not a problem. Don't use the hammerite, it's crapola. 

Edited July 8, 2022 by blackrose

[Bargebuilder]

2 hours ago, Marc Pyn said:

Hi folks,

Had a survey when buying boat which said gas locker needs painting and recommended jotun 87. Bought 5L and preparing surface by scraping loose rust and then today trying the angle grinder / cup brush with mask / goggles / long sleeves in the hope to better prep.

 

1st question is - am I OK to bring it back to bare metal without any fear of going through the sides or bottom using this grinder & is this required for jotun epoxy? Steel doesn't bend when I stand / slightly bounce where gas bottle is in pic 1 but some areas are not coming off with scraper - pic 2 shows what came up with some of the bigger bits.

 

I'd like to reduce the amount of power tools in here if scrapers and wire brush are enough, though they arent getting back bare metal just loose stuff. Using grinder for a few mins last night created a lot more loose stuff quickly & quite forcefully getting back to metal shown at bottom of pic 3. With pic 4 zoomed out view. I can kneel outside the gas locker to better use the tool but concerned I don't want to put too much pressure on the surface. I'm not sure what's underneath but from other forum posts there will be some lining / space between this locker and the baseplate / hull sides? 

 

I'm not using valcan rust converter which I've seen mentioned on different posts -  just planning on the epoxy tomorrow as session is booked in with my dad who has lot more painting experience but not with epoxy itself. He was told by a decorator at bowls not to use epoxy in such unventilated small areas so the other question is - is it safe for me to be inside the locker and paint wearing a mask as it says on the spec sheet to use in well ventilated area and don't ingest  fumes.

 

We do have 2 tins of hammerite, so if that's as effective and less dangerous then we won't open the epoxy for this job.

 

We also have a fan which we could use and some DIY long handles so potentially could paint from outside but not sure what we have will work and fumes still be coming upwards. 

 

From outside i can point my head sidewards and with a longer handle reach a fair amount to paint 'blind' so to speak, so I'm hoping that, as we are not looking for a good finish, this may be a safer approach to get the first layer on with paintbrushes to enough of a thickness - making a visual check in between each go?

 

And 3rd question is - it OK to hose down the areas when I've finished preparing today to try and flush out more of the dust or is this a bad idea for any reason with some / all areas on floor being back to bare steel. The dust seems endless when I use the dustpan and i could use a sponge with some sugar soap or detergent if thats better? We also have methylated spirit advised by the jotun seller to use in place of white spirit before applying the 1st coat so will be wiping the surface down in morning before painting.

 

Hope that makes sense & many thanks for sharing any insight / experience. 

Also pic of the ppe I have available 

All the problems and concerns that you have mentioned would not be issues at all if your surveyor had recommended the correct coating for such a job. You are making life unnecessarily difficult for yourself!

 

Cup brush preparation is good enough and in many cases an ordinary wire brush will be sufficient and being solvent free it shouldn't kill you either!

 

Get 5Kg of this stuff:

 

Epo-chem™ RS 500P is a unique solvent-free, wet & rust tolerant epoxy primer or primer/finish protective coating.

The system’s long-term performance is based on completely sealing the surface and arresting the rust totally.

 

[Marc Pyn]

21 minutes ago, blackrose said:

 

I'd prep and paint up the sides by a couple of inches of I were you.

 

Vacuum out the area after getting it all back to bare steel. If you're going to spirit wipe before painting then use Jotun thinners 17 which is the recommended thinners for Jotamastic 87. Note: the fumes from the thinners are pretty bad in a confined space. 

 

I usually thin the first coat of the Jotamastic with no more than 10% thinners to make sure it gets into all the pits but that's not imperative, just stipple the first coat in well with the brush. If you do thin the paint with thinners 17 then do it after mixing paint and hardener, not at the same time.

 

Pay attention to the mixing ratios and overcoating times given in the technical data sheet for the paint. Are you using standard or winter grade hardener? 

 

I put 3 coats of Jotamastic 87 on my gas locker floor. No problems with fumes. I put a large rubber scraper mat with holes down onto the floor after the paint had fully cured to protect the paint from scraping gas bottles. My gas locker regularly gets flooded as the vents are only a few inches above the waterline, but now it's not a problem. Don't use the hammerite, it's crapola. 

Thanks Blackrose. We are using the standard version. We don't unfortunately have time to get the thinners so would you still advise using meths spirit to wipe down any remaining dust from the area before applying first coat? The tech support jotun retailer said to use that and not white spirit. 

 

Glad to hear there's no issue with fumes while painting inside the lockers from the 87. Do you have the same location for your gas locker as ours - so you have to do some  contortionist moves to get your head inside? 

 

And on a very sunny day like tomorrow do we need to leave it 24 hours before 2nd coat or might i be able to start again in the eve if finish coat 1 in the morning? 

 

 

[Marc Pyn]

5 minutes ago, Bargebuilder said:

All the problems and concerns that you have mentioned would not be issues at all if your surveyor had recommended the correct coating for such a job. You are making life unnecessarily difficult for yourself!

 

Cup brush preparation is good enough and in many cases an ordinary wire brush will be sufficient and being solvent free it shouldn't kill you either!

 

Get 5Kg of this stuff:

 

Epo-chem™ RS 500P is a unique solvent-free, wet & rust tolerant epoxy primer or primer/finish protective coating.

The system’s long-term performance is based on completely sealing the surface and arresting the rust totally.

 

Thanks Boat builder - that looks very useful stuff. We have session booked in for tomorrow so won't be possible to get anything else before then. Aside from the extra prep time and it being solvent free is there any difference to the outcome from using the 87 in terms of long term protection? 

[Bargebuilder]

The advantage of the Chemco product is that it is designed to cover, stick to and arrest the development of rust. It will stay put, not flake off and rust won't push its way through. 

 

Other epoxy products can be excellent, but their effectiveness depends on a very much higher standard of preparation. Unless all rust is removed before application, the job will look great initially but in time the rust may emerge.

 

Either product should be tough enough to resist abrasion, but a mat under your bottles will give added protection. The concern is, will both still be protecting the steel from corrosion in a couple of years time.

[Marc Pyn]

1 hour ago, Bargebuilder said:

The advantage of the Chemco product is that it is designed to cover, stick to and arrest the development of rust. It will stay put, not flake off and rust won't push its way through. 

 

Other epoxy products can be excellent, but their effectiveness depends on a very much higher standard of preparation. Unless all rust is removed before application, the job will look great initially but in time the rust may emerge.

 

Either product should be tough enough to resist abrasion, but a mat under your bottles will give added protection. The concern is, will both still be protecting the steel from corrosion in a couple of years time.

Thanks boatbuilder. That's the question - with good prep does the 87 create much better protection for future as thats the main aim of the job and why surveyor said he recommended that particular one. (Will be using rubber mats as standard for putting gas bottles on re abrasion) Can't seem to find a supplier of the other one other than there main site but will continue with cup brush prep now I've started. 

[Bargebuilder]

Chemco make the stuff and supply it themselves at trade prices in tins of 5Kg or 1Kg sample tins. Two pack of course.

 

The Chemco is likely to stick better unless the prep is to bright metal with no rust or gingering so is also likely to last longer.

 

They have a superb technical team at the end of the phone who will offer excellent advice. 

[blackrose]

2 hours ago, Bargebuilder said:

All the problems and concerns that you have mentioned would not be issues at all if your surveyor had recommended the correct coating for such a job. 

 

There is more than one way to skin a cat. His surveyor did recommend the correct coating for the job in my opinion and I've used Jotamastic epoxies professionally. It's excellent stuff if used correctly. 

Edited July 8, 2022 by blackrose

[Bargebuilder]

1 minute ago, blackrose said:

I've used Jotamastic epoxies professionally. It's excellent stuff if used correctly

Without a doubt, but as a professional you will know how unlikely it is that one could achieve a grit blast type preparation on the type of scale and corrosion in the photo with just a cup brush and angle grinder, particularly in the corners.

[blackrose]

1 hour ago, Bargebuilder said:

Without a doubt, but as a professional you will know how unlikely it is that one could achieve a grit blast type preparation on the type of scale and corrosion in the photo with just a cup brush and angle grinder, particularly in the corners.

 

If you read the TDS for the product you'll find that power tool steel prep is perfectly acceptable for Jotamastic 87. It's very surface tolerant. 

This was the prep I did on my rusty stern lockers with wire wheels and cup brush on an angle grinder and smaller wire brush on a drill to get into the corners. Look how badly pitted it is. My prep isn't perfect and it probably needs another going over, but that sort of preparation standard (SA 2.5) is fine for Jotamastic. In other words if you know what you're doing and put some effort into it you can get into the corners and you don't need a grit blasted finish.

 

The most important thing for the OP is to make sure you're removing rust scale rather than just polishing it with the wire wheel because polished rust scale can look like good steel. But hit it with a welders chipping hammer and it will come off.

 

Edited July 8, 2022 by blackrose

[blackrose]

2 hours ago, Marc Pyn said:

Thanks Blackrose. We are using the standard version. We don't unfortunately have time to get the thinners so would you still advise using meths spirit to wipe down any remaining dust from the area before applying first coat? The tech support jotun retailer said to use that and not white spirit. 

 

Glad to hear there's no issue with fumes while painting inside the lockers from the 87. Do you have the same location for your gas locker as ours - so you have to do some  contortionist moves to get your head inside? 

 

And on a very sunny day like tomorrow do we need to leave it 24 hours before 2nd coat or might i be able to start again in the eve if finish coat 1 in the morning? 

 

 

 

Personally I wouldn't spirit wipe unless I was using the correct thinners but that's just me. Maybe meths is ok but I thought Jotun thinners 17 was xylene based.

 

Some people argue that all you're doing when spirit wiping is moving the dirt and grease around. Whereabouts are you? I could bring some thinners 17 over if you're nearby. If not I'd just vacuum thoroughly and wipe with a clean dry cloth. Make sure your shoes aren't dirty when you get in the locker to paint.

 

The mixing ratios for Jotamastic 87 is 6 parts paint to one part hardener and at these temps minimum overcoating time is 10 hours. BUT if your steel is in contact with water it will be colder so I'd leave it for 24 hours before overcoating.

 

Those are the application guidelines for the basic Jotamastic 87. If you've got the version with aluminum flake let me know and I'll find the correct application guidelines. 

 

Edited July 8, 2022 by blackrose

[Marc Pyn]

Thanks so much blackrose for all the info & boatbuilder and everyone else who's posted. Very much appreciated. 

[dmr]

4 hours ago, blackrose said:

 

If you read the TDS for the product you'll find that power tool steel prep is perfectly acceptable for Jotamastic 87. It's very surface tolerant. 

This was the prep I did on my rusty stern lockers with wire wheels and cup brush on an angle grinder and smaller wire brush on a drill to get into the corners. Look how badly pitted it is. My prep isn't perfect and it probably needs another going over, but that sort of preparation standard (SA 2.5) is fine for Jotamastic. In other words if you know what you're doing and put some effort into it you can get into the corners and you don't need a grit blasted finish.

 

The most important thing for the OP is to make sure you're removing rust scale rather than just polishing it with the wire wheel because polished rust scale can look like good steel. But hit it with a welders chipping hammer and it will come off.

 

I think you've posted this picture before so I will repeat my comment, "thats very nice prep".  Mine was almost as good as this, though I confess I paid/bribed Goliath to do this for me, I just did the painting. I used Reactive Resins Armourguard rather than Jotun but its stayed on perfectly. Both are "surface tolerant" epoxy primers so should be fine with this level of prep, in fact the surface texture probably helps. Both can cope with a small amount of rust left in the pits.

[dmr]

9 hours ago, Chewbacka said:

I personally would not use acetone in a poorly ventilated enclosed space.  The fumes could incapacitate you, it’s highly flammable and at the right mix of vapour to air can explode with a small spark.

Acetone is still my cleaner/degreaser of choice but I should have mentioned the H&S aspects. Its good because its volatile (hope its not too bad for the planet) so you don't have to worry about solvent compatibility. Stick a bit on some "blue paper" and scrub till the paper no longer turns black. Repeat as required. Keep your head in fresh air etc etc. Do not just pour tons of the stuff into a confined space, and put the lid back on everytime you use it. I am aware of a fatality where a youngster on a job scheme spilled a whole pot in a relatively small room. Treat all solvents with respect, including paints.

[agg221]

If you are stuck using wire brushes, one observation is that drill-mounted brushes can help with scale removal, sometimes better than angle grinder mounted ones. Easily available from Screwfix or similar. The advantage is that when the wires start to get knocked one way so they are rubbing rather than cutting you can reverse the drill and they start cutting again. I find all except the stiffest twisted wire angle grinder brushes tend to start polishing the rust in time.

 

It does help to get everything clean and degreased before painting. Given the weather forecast I would be inclined to use a good detergent in water rather than a solvent - plenty of time for it to dry before you apply the first coat. I would also consider using a phosphoric acid rust converter before painting as it will take out a lot of the rust you can't get to down the pits. Any car spares place is likely to have some off the shelf if Screwfix doesn't have anything suitable. These are a case of apply once the surface is degreased, then wipe off the excess and allow to dry. Optionally you can then go over it again wire brush off most of the converted material, leaving converted areas you can't hit and allowing you to check that no more powdery brown rust is revealed, which is a sign that you haven't yet gone deep enough, in which case repeat until no powdery brown rust is produced.

 

Alec

[Bargebuilder]

9 hours ago, agg221 said:

If you are stuck using wire brushes, one observation is that drill-mounted brushes can help with scale removal, sometimes better than angle grinder mounted ones. Easily available from Screwfix or similar. The advantage is that when the wires start to get knocked one way so they are rubbing rather than cutting you can reverse the drill and they start cutting again. I find all except the stiffest twisted wire angle grinder brushes tend to start polishing the rust in time.

 

It does help to get everything clean and degreased before painting. Given the weather forecast I would be inclined to use a good detergent in water rather than a solvent - plenty of time for it to dry before you apply the first coat. I would also consider using a phosphoric acid rust converter before painting as it will take out a lot of the rust you can't get to down the pits. Any car spares place is likely to have some off the shelf if Screwfix doesn't have anything suitable. These are a case of apply once the surface is degreased, then wipe off the excess and allow to dry. Optionally you can then go over it again wire brush off most of the converted material, leaving converted areas you can't hit and allowing you to check that no more powdery brown rust is revealed, which is a sign that you haven't yet gone deep enough, in which case repeat until no powdery brown rust is produced.

 

Alec

That is all excellent advice and I'm sure will result in a prepared surface suitable for most coatings, but all that time and effort can very easily be avoided by using a coating designed to cover and arrest the development of rust with much, much less work and no need for acids or solvents; Epo-chem™ RS 500P

[agg221]

2 hours ago, Bargebuilder said:

That is all excellent advice and I'm sure will result in a prepared surface suitable for most coatings, but all that time and effort can very easily be avoided by using a coating designed to cover and arrest the development of rust with much, much less work and no need for acids or solvents; Epo-chem™ RS 500P

I too use Chemco products and am very happy with the combination of performance and price. Where I feel it's pushing them beyond the limits is when the rust has formed sheets. The structure of this particular type of rust is laminations, alternating between a thick layer of material which can look almost like metal and a thin layer of conventional looking red/brown rust. The problem is that, with time, oxygen and water they all convert to the crumbly type of rust. To give long-term protection you have to be confident that the paint either forms a perfect seal, or that the bond between the paint and the surface does not allow undercutting. The Chemco surface tolerant primer does give excellent bonding to a rusty surface and stops undercutting between the paint and the surface but if the rust layer is thick enough to allow delamination within the rust itself, the whole lot will eventually come off in sheets if the paint is breached, so you are relying on perfect encapsulation. This is the way powder coating eventually fails for example. This is why I prefer to go for surface preparation which removes all sheet rust as I am not confident that my paintwork will be that perfect. Once the sheet rust is gone, some remaining well bonded thin rust will not reduce the life expectancy of the coating, hence when touching up the rubs and scuffs on the outside of the boat I just use a hand wire brush to remove anything loose and put the Epo-chem RS 500p straight on.

 

Alec

[dmr]

This chemco stuff sounds too good to be true (😀). I might get some and give it a go, but if its so good why does everybody keep using Jotun and International etc???? I had a look at their website but its "corporate" rather than technical.