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Thread: filling over epoxy on an aluminium saltwater boat

  1. #1
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    Default filling over epoxy on an aluminium saltwater boat

    Im doing about 20 spot repairs as this boat is already suffering corrosion issues.

    original builder used filler directly on aluminium in certain areas, some of that is lifting off / bubbling with corrosion.

    also paint bubbling up where filler was not used. usually near an edge or drilled hole.

    after grinding/sanding i plan to recoat with a 2 part epoxy Strontium Chromate primer (Carboline Altra Bond 3094), followed by a 2 part epoxy undercoat (Altex Barrier Undercoat)

    I've had great success with the above before on corroded alloy around saltwater, so i don't want use anything else. allready have product.

    Topcoat will be 2K

    So, the questions;

    what are everyones thoughts of me using the filler on top of the undercoat?

    are some fillers better for that purpose?

    Filler i have is CAR SYSTEM ELASTIC WEISS. polyester fine filler.

    I do not want to put filler directly on the alloy, that's been a fail already.

    have read many posts saying dont do it as all filler manufacturers say put DIRECT ON METAL, but my way of thinking for this situation is put it over the epoxy or dont use it all.

    Help

    Mark

  2. #2
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    Hi Mark
    If we were doing it here we would probably use a "good" epoxy primer on the bare aluminum after scuffing it with some 220 then scuff it again before the application of the filler. I would use a mixture of milled fiberglass filler and liquid fiberglass resin which makes the filler more liquid so that the filler gets into scratches and bonds better with the surface.

    Using "good" primer and paint products will help the repairs hold up.

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    i think it depends on the use of the boat to an extent. there's a ton of fairing compounds to choose from, but are the areas going to be under water? is it a trailer boat and hauled out after each outing?
    in addition to what len said, there are some epoxy based putties like this: https://www.fibreglast.com/product/M...ling-compounds
    i've used both milled glass filler and epoxy compounds on my boats with good success, but for fillers that live under water all the time, i like the epoxy based compounds. they don't sand as easy as claimed though. but once bottom paint is on you can't tell.
    b marler

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    Quote Originally Posted by bmarler View Post
    i think it depends on the use of the boat to an extent. there's a ton of fairing compounds to choose from, but are the areas going to be under water? is it a trailer boat and hauled out after each outing?
    in addition to what len said, there are some epoxy based putties like this: https://www.fibreglast.com/product/M...ling-compounds
    i've used both milled glass filler and epoxy compounds on my boats with good success, but for fillers that live under water all the time, i like the epoxy based compounds. they don't sand as easy as claimed though. but once bottom paint is on you can't tell.
    I'm glad you chimed in, I don't have nearly as much experience on boats as you do.

    If price is any indication of quality that Fibreglast filler must be good stuff.

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    Quote Originally Posted by Len View Post
    I'm glad you chimed in, I don't have nearly as much experience on boats as you do.

    If price is any indication of quality that Fibreglast filler must be good stuff.
    i buy quite a few different things from fibreglast. vacuum bagging supplies, release agent, resins and cloth. it's not the cheapest, but the quality is good. you know as well as i do that quality materials make the difference if you want to have a lasting finish.
    b marler

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    Quote Originally Posted by bmarler View Post
    i think it depends on the use of the boat to an extent. there's a ton of fairing compounds to choose from, but are the areas going to be under water? is it a trailer boat and hauled out after each outing?
    in addition to what len said, there are some epoxy based putties like this: https://www.fibreglast.com/product/M...ling-compounds
    i've used both milled glass filler and epoxy compounds on my boats with good success, but for fillers that live under water all the time, i like the epoxy based compounds. they don't sand as easy as claimed though. but once bottom paint is on you can't tell.
    I should have said its trailered and all repair areas are above water line.

    Ok thats a great idea, epoxy fairing over the epoxy undercoat.

    Can i spray 2K topcoat straight over the epoxy fairing?

    Cant find that 4118 here in australia, have to find an equivalent.
    Last edited by Mark 63; 03-23-2022 at 10:28 PM.

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    Quote Originally Posted by Mark 63 View Post
    I should have said its trailered and all repair areas are above water line.

    Ok thats a great idea, epoxy fairing over the epoxy undercoat.

    Can i spray 2K topcoat straight over the epoxy fairing?

    Cant find that 4118 here in australia, have to find an equivalent.
    Most epoxy primers have a "re-coat window" which tells you how long you have to spray your paint on top without sanding. Some epoxy primers have a 4 hour window and some have a much longer time window. Once you are beyond that time you should sand/scuff the surface before painting. Of course higher temperatures can shorten you re-coat window. Read the technical data for the primer you're using.

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    Quote Originally Posted by Mark 63 View Post
    I should have said its trailered and all repair areas are above water line.

    Ok thats a great idea, epoxy fairing over the epoxy undercoat.

    Can i spray 2K topcoat straight over the epoxy fairing?

    Cant find that 4118 here in australia, have to find an equivalent.
    it's never a good idea to shoot topcoat directly over fillers. they have different absorption characteristics and will show through. i haven't used the epoxy undercoat you're using so can't advise on the recoat window for it, but if you've got a lot of repair areas be prepared to do some sanding.
    another idea might be to spot repair, (shoot some undercoat on the problem areas, then fill and level them) then put your full coat of undercoat over the repairs and rest of the hull.
    while i like the all epoxy approach, since you're on a trailerable boat and the repairs are all above the waterline, you can use just about any filler you want. you're sealing it with epoxy anyway. i'd stick with waterproof fillers though for the added level of protection.
    aluminum does present it's own set of challenges for sure, but the path you're on is a good one. i wouldn't put filler on the bare aluminum either, epoxy is the way to go.
    it's tough to recommend products when you're in a different geographical area, i have a friend that restores cars where you're at, and we have many discussions about what products he can get that would be similar to what i use here. not like an apples to oranges discussion, more like red apples to green ones...
    b marler

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    Quote Originally Posted by bmarler View Post
    it's never a good idea to shoot topcoat directly over fillers. they have different absorption characteristics and will show through. i haven't used the epoxy undercoat you're using so can't advise on the recoat window for it, but if you've got a lot of repair areas be prepared to do some sanding.
    another idea might be to spot repair, (shoot some undercoat on the problem areas, then fill and level them) then put your full coat of undercoat over the repairs and rest of the hull.
    while i like the all epoxy approach, since you're on a trailerable boat and the repairs are all above the waterline, you can use just about any filler you want. you're sealing it with epoxy anyway. i'd stick with waterproof fillers though for the added level of protection.
    aluminum does present it's own set of challenges for sure, but the path you're on is a good one. i wouldn't put filler on the bare aluminum either, epoxy is the way to go.
    it's tough to recommend products when you're in a different geographical area, i have a friend that restores cars where you're at, and we have many discussions about what products he can get that would be similar to what i use here. not like an apples to oranges discussion, more like red apples to green ones...
    Thanks B
    Ok ill shoot the Epoxy Barrier Undercoat over the filler
    The filler i already have is Polyester, surely i cant use that?

    Edit;
    Update i rang the ALTEX rep that supplied me the primer & UC, very helpful man. Dont know why i didn't do that first.

    He has an epoxy fairing/filler, easy to sand. ill get a 2 litre pack tomorrow. ALTEX EPOXY SPOT FILLER.

    says its not just a spot filler, its a wide area fairing compound but they dont like to put that on the can. Too much litigation from incorrect installation on superyachts.

    He talked me thru the whole process and confirmed everything you guys have told me.

    Mark
    Last edited by Mark 63; 03-25-2022 at 12:40 AM. Reason: I rang the Rep

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    Quote Originally Posted by Mark 63 View Post
    Thanks B
    Ok ill shoot the Epoxy Barrier Undercoat over the filler
    The filler i already have is Polyester, surely i cant use that?

    Edit;
    Update i rang the ALTEX rep that supplied me the primer & UC, very helpful man. Dont know why i didn't do that first.

    He has an epoxy fairing/filler, easy to sand. ill get a 2 litre pack tomorrow. ALTEX EPOXY SPOT FILLER.

    says its not just a spot filler, its a wide area fairing compound but they dont like to put that on the can. Too much litigation from incorrect installation on superyachts.

    He talked me thru the whole process and confirmed everything you guys have told me.

    Mark
    ok, sounds like you have it figured out. i have known people to use polyester fillers above the waterline, but i don't do it. too much chance of failure for me to chance it. you have the right products coming, and using a system recommended by the rep that's supplying the other products pretty much guarantees good compatibility.
    for marine use, the all epoxy approach is best. good luck with it!
    b marler

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    Quote Originally Posted by bmarler View Post
    ok, sounds like you have it figured out. i have known people to use polyester fillers above the waterline, but i don't do it. too much chance of failure for me to chance it. you have the right products coming, and using a system recommended by the rep that's supplying the other products pretty much guarantees good compatibility.
    for marine use, the all epoxy approach is best. good luck with it!
    Primer, undercoat and the new Fairing compound went well.

    Im just about to apply the last sealing coat over the fairing.

    but Im working outside (undercover) and constant rain for another week.

    ide say humidty close to 100%

    am concerned about applying the finish top coat in these conditions.

    I do have a few heat lamps will that be enough?

  12. #12
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    Certainly not ideal conditions. The humidity is not the biggest factor. I can't remember if you mentioned the temperature or not.
    My thinking would be that if you don't get dew on it in the morning you're probably ok as long as the temps are reasonable. If you have a hygrometer to double check the humidity in there it would be even better.
    If it's really 100 percent humidity I might hold off.
    The tds of the product you're using should say max humidity. You're usually ok to push it a little, but I'd be wary to waste all that work if conditions are just too bad.

    ok, that was a pretty wishy-washy post wasn't it? was posting from my phone and that's not ideal.
    anyway, you have a few of things to consider. obviously the temperature and humidity, and then there's the recoat window.
    at this point, all the products you have on it are epoxy based, so it can sit until conditions are more favorable if need be. the only downside to letting it sit is that you're going to be out of the recoat window and that means more sanding before applying anything new.
    the tds for the product you use will have temperature and humidity values for you to use as a guide to let you know if it's safe to apply their products. it's always best to document these things as you go in case there's any issue with the material that might fall under a warranty. (although it's usually only to get more materials from them due to some defect)
    it's approaching fall down there now, and temps will start falling off (i think). hopefully you still have enough of a weather window to get it done before conditions really fall off in regards to outside work.
    i mentioned earlier, you can push the temps and humidity a little and still be safe enough, but keep it within limits. i'm not familiar with the products you're using so i can't say what the limits might be, but most epoxy likes 85% or lower. a hygrometer is your friend here, and you might be pleasantly surprised to see it's lower than you think where the boat is under the cover. truth be told, i've applied epoxy up to 95% humidity without issues, but i did it on a warm day and it kicked pretty fast.
    temperature is more important than humidity. we usually shoot the surface with an infrared thermometer before painting. i try to keep things above 60f for the cure cycle.
    lastly is the recoat window. read the tds to see what they recommend for recoat. usually if you are within the window you can shoot without sanding. if you're out, then some manufacturers recommend sanding, re-applying the same coating, then moving on to the next thing. some just recommend to sand and move on. you'll need to read up on your particular material.
    sorry for the long post, hope it was helpful.
    Last edited by bmarler; 03-28-2022 at 08:27 PM. Reason: more, better info
    b marler

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    Quote Originally Posted by bmarler View Post
    Certainly not ideal conditions. The humidity is not the biggest factor. I can't remember if you mentioned the temperature or not.
    My thinking would be that if you don't get dew on it in the morning you're probably ok as long as the temps are reasonable. If you have a hygrometer to double check the humidity in there it would be even better.
    If it's really 100 percent humidity I might hold off.
    The tds of the product you're using should say max humidity. You're usually ok to push it a little, but I'd be wary to waste all that work if conditions are just too bad.

    ok, that was a pretty wishy-washy post wasn't it? was posting from my phone and that's not ideal.
    anyway, you have a few of things to consider. obviously the temperature and humidity, and then there's the recoat window.
    at this point, all the products you have on it are epoxy based, so it can sit until conditions are more favorable if need be. the only downside to letting it sit is that you're going to be out of the recoat window and that means more sanding before applying anything new.
    the tds for the product you use will have temperature and humidity values for you to use as a guide to let you know if it's safe to apply their products. it's always best to document these things as you go in case there's any issue with the material that might fall under a warranty. (although it's usually only to get more materials from them due to some defect)
    it's approaching fall down there now, and temps will start falling off (i think). hopefully you still have enough of a weather window to get it done before conditions really fall off in regards to outside work.
    i mentioned earlier, you can push the temps and humidity a little and still be safe enough, but keep it within limits. i'm not familiar with the products you're using so i can't say what the limits might be, but most epoxy likes 85% or lower. a hygrometer is your friend here, and you might be pleasantly surprised to see it's lower than you think where the boat is under the cover. truth be told, i've applied epoxy up to 95% humidity without issues, but i did it on a warm day and it kicked pretty fast.
    temperature is more important than humidity. we usually shoot the surface with an infrared thermometer before painting. i try to keep things above 60f for the cure cycle.
    lastly is the recoat window. read the tds to see what they recommend for recoat. usually if you are within the window you can shoot without sanding. if you're out, then some manufacturers recommend sanding, re-applying the same coating, then moving on to the next thing. some just recommend to sand and move on. you'll need to read up on your particular material.
    sorry for the long post, hope it was helpful.
    thanks B

    yeh this rain is relentless. non stop for 6 weeks now, & 7 day forecast is same.

    cant wait as boat owner needs boat next week.

    I finisned all epoxys last night, im using heatlamps to warm up the spot repair areas, although i have to keep moving them around as i only have 3.

    topcoat today, very nervous.

    cant find data sheet for my topcoat.

    all i know is its 2:1 2K by Europa paints Sylvania.

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    Quote Originally Posted by Mark 63 View Post
    thanks B

    yeh this rain is relentless. non stop for 6 weeks now, & 7 day forecast is same.

    cant wait as boat owner needs boat next week.

    I finisned all epoxys last night, im using heatlamps to warm up the spot repair areas, although i have to keep moving them around as i only have 3.

    topcoat today, very nervous.

    cant find data sheet for my topcoat.

    all i know is its 2:1 2K by Europa paints Sylvania.
    not sure how you paint something where you don't have a data sheet on it. the data sheet (tds) gives all the parameters that the coating has been tested and approved for application. i might have chosen something else to apply. how do you know what reducers to use to get the viscosity fine tuned? or the recoat times? just guessing is a little risky, but good luck to you!
    b marler

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    Quote Originally Posted by bmarler View Post
    not sure how you paint something where you don't have a data sheet on it. the data sheet (tds) gives all the parameters that the coating has been tested and approved for application. i might have chosen something else to apply. how do you know what reducers to use to get the viscosity fine tuned? or the recoat times? just guessing is a little risky, but good luck to you!
    Yeh i got a verbal from the supplier for thinning and recoat timing, humidity and temp wasnt on my mind then.

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