TK01

Chasing Electrolysis

15 posts in this topic

Hi guys

I've got a bit of a dilemma with my old quintrex hull.  It's a mid 80's model fishfinder centre console.  About 3 years ago I gave it a full makeover and did the majority of the work myself.  One job that I didn't take on was painting it.  I did all the prep work myself and spent many hours sanding to get it ready for the painter.  I left the original paint on but there were patches of bare metal all over the place including some larger sections where I built a frame for a cast deck in the bow.  He was going to clean it with prepsol, etch prime and paint.

It became evident not long after getting the boat home that the 'professional' that I paid to do the job did a dodgy job.  There were bits of masking tape that he had left on the hull and painted over.  As time went by I also found that he did not even etch prime the bare patches despite telling me that's what he would do.  I don't know if he cleaned it up properly either and my guess is probably not judging by the rest of his job.  3 years on and there are now patches of bubbling/cracking paint all over the place and I'm not sure what to do.  Do I:

  • Just leave it and keep fishing until it starts to fall apart?
  • Rub back the ugly bits and do a touch up job, knowing that I will probably be doing this over and over as new spots arise?
  • Just sell it and buy another boat?
  • Pull the whole thing apart and get a real professional to do it properly this time?  My worry is that the damage has been done to the aluminium now and no amount of proper cleaning and priming before painting will give any certainty that I won't be facing this exact same problem in a couple of years.

What would you do?

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Never repainted an aluminium hull before but how hard can it be? I'm sure there is some chemical that will help you get quickly back to bare metal. Then you can prep and paint it properly. DIY you'll save $$ and know it's done properly.

it can't be harder than what some idiot did at a place I bought a few years back. He covered beautiful Blackwood floorboards with a crappy brown glue and cheap carpet. It took me 5 days, two drills 15 metal orbital heads and some damn noxious chemicals to remove it. Looked amazing though once it was done and very rewarding.

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Hi Luke

I think it's a pretty big job.  It's not just the painting, pulling it apart and the refit are also part of the job and having done it all before I break into a cold sweat just thinking about taking it on again, but it certainly is an option that I haven't ruled out as yet. 

The corrosion issue bothers me.  I don't want to do all that work if it's not going to be a high certainty that the corrosion won't just start again in a couple of years.

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Hi TK01,

I don't own an alloy boat but have some experience with painted alloy as the pod and marlin board on my boat are alloy...I agree the pull apart and refit are probably as big a job as the prep and painting. That's why when I changed over the motor I took the opportunity to have the pod repainted - I used a car smash repairer to sand blast, etch prime and 2 pack spray the pod while still mounted to the boat. But after 17yrs of use I now have the inevitable dings and scratches and some blistering paint spots... I am not really concerned as to me its largely an aesthetic thing.

Are you concerned that without paint your boat will corrode quicker?  From my perspective, there are many bare alloy boats out there - infact most commercial fisherman, oyster farmers etc run bare alloy. The alloy itself produces a dull coating (oxidisation) that in general prevents further corrosion. Its this oxidisation process that is blistering your paint...but it is also protecting the underlying metal. So I don't think any real damage has been done to the hull by flaking paint. The damage usually comes from electrolysis/galvanic corrosion where you have non alloy metals in contact with the hull eg: fittings to the hull that are incorrectly mounted without sealants inbetween, or old sinkers lying in contact with the alloy hull - and that type of corrosion can even happen where you drill through painted surfaces. Or from acidic liquids sitting in contact with the alloy for prolonged periods - this can manifest as a pinhole or cheese cloth perforated area on the alloy.

So maybe scrape away some of the flaking and have a good look at the underlying alloy as I think the first thing you would want to be comfortable with is that the boat structure has not been compromised.

Perhaps some raiders with bare alloy boats can chip in and share their experiences !

Once comfortable with that, evaluate do you like the boat, the way it handles and does it meet your fishing requirements? If it does maybe lean toward keeping it. 

Regarding aesthetics, if you want to minimize the work but are concerned about aesthetics have you considered:

1) work around the fit out and go back to bare alloy

2) go bare alloy bottom of hull and paint top sides

Anyway, I feel for ya! ... putting in so much work into your pride and joy  and being let down by the guy you hired must feel like the pits.

Best of luck.

Zoran

 

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2 hours ago, zmk1962 said:

Hi TK01,

I don't own an alloy boat but have some experience with painted alloy as the pod and marlin board on my boat are alloy...I agree the pull apart and refit are probably as big a job as the prep and painting. That's why when I changed over the motor I took the opportunity to have the pod repainted - I used a car smash repairer to sand blast, etch prime and 2 pack spray the pod while still mounted to the boat. But after 17yrs of use I now have the inevitable dings and scratches and some blistering paint spots... I am not really concerned as to me its largely an aesthetic thing.

Are you concerned that without paint your boat will corrode quicker?  From my perspective, there are many bare alloy boats out there - infact most commercial fisherman, oyster farmers etc run bare alloy. The alloy itself produces a dull coating (oxidisation) that in general prevents further corrosion. Its this oxidisation process that is blistering your paint...but it is also protecting the underlying metal. So I don't think any real damage has been done to the hull by flaking paint. The damage usually comes from electrolysis/galvanic corrosion where you have non alloy metals in contact with the hull eg: fittings to the hull that are incorrectly mounted without sealants inbetween, or old sinkers lying in contact with the alloy hull - and that type of corrosion can even happen where you drill through painted surfaces. Or from acidic liquids sitting in contact with the alloy for prolonged periods - this can manifest as a pinhole or cheese cloth perforated area on the alloy.

So maybe scrape away some of the flaking and have a good look at the underlying alloy as I think the first thing you would want to be comfortable with is that the boat structure has not been compromised.

Perhaps some raiders with bare alloy boats can chip in and share their experiences !

Once comfortable with that, evaluate do you like the boat, the way it handles and does it meet your fishing requirements? If it does maybe lean toward keeping it. 

Regarding aesthetics, if you want to minimize the work but are concerned about aesthetics have you considered:

1) work around the fit out and go back to bare alloy

2) go bare alloy bottom of hull and paint top sides

Anyway, I feel for ya! ... putting in so much work into your pride and joy  and being let down by the guy you hired must feel like the pits.

Best of luck.

Zoran

 

Well said mate.In my opinion bare alloy is the way to go like Zoran said.I bought and kept my tinny bare alloy for many reasons mentioned.The thing to remember is to run all earth's through a busbar or directly to the battery negative to prevent issues such as electrolysis.Keeping dissimilar metals seperate from your hull will prevent Galvonic corrosion also.

  As for what to do in your case only you can decide on that one.Too many people are focused on how things look these days instead of functionality (Nothing wrong with that)I can't be bothered impressing anyone and  choose the later to prevent the headaches you are experiencing.

Without any photos it's almost impossible to help you more than that.

Chuck some photos up and let us see if we can help further.

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Thanks a lot for these responses guys, very helpful!

I hadn't really considered the bare aluminium option this time around.  I remember mulling over it 3 years ago but decided on paint mainly because I thought it would look better and meant I didn't need to get the hull back to bare alloy in the prep stage.  In hindsight I think I made the wrong decision.

You've got me thinking now though.  I think the majority if not all of the bubbling/cracking is on the gunwales at the moment.  I was talking to my wife at lunch today about the advice you guys have given and she said 'well, why don't you just strip those bits back to bare metal and leave the rest of it painted.  That way you don't have to pull the whole boat apart.'  Oh my god!  That might even look cool.  The bottom of the hull is already bare alloy so it would blend in quite nicely.

I'll take some photos tonight to show you the issue.  Will also have a closer look to see if I'm not mistaken about the gunwales being the only affected area.

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51 minutes ago, TK01 said:

....

The bottom of the hull is already bare alloy so it would blend in quite nicely.

....

What's this "blend in" ... it sounds so compromising... mate it would be "CUSTOM" .... just the way you wanted it !!!

Cheers

Zoran

PS - will keep an eye out for the photos.

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A couple of pics as promised. That fuel filler is by far the worst part.

 

6871784D-922A-4C3F-A84E-8846CE16FC48.jpeg

D5517443-4C66-4470-A5D3-D08F68247EA4.jpeg

40917DD2-AC5D-4515-A0BB-69A2E6989CA4.jpeg

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Mate... to me it looks fine and I personally would not worry about it for quite a while. Go fishing more !

But if it bothers you, inspect around the fuel filler - seems to be corroding more than other parts - there may be some metal to alloy contact there or it could just be the crevice that holds moisture. 

Personally I'd go bare alloy in around the fuel filler, and just touch up (or go bare) gunwales over time.

I keep this link for whenever I want to refresh my understanding of corrosion -  https://www.clubmarine.com.au/internet/clubmarine.nsf/docs/MG19-5+Technical

Cheers

Zoran

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I have to be honest and say that is a terrible paint job mate.The photo of what looks like the gunnel hasn't even got proper paint coverage(Looks like it was painted with thinned liquid paper) adjacent to the bubbling.

  That fuel filler surround that is riveted looks like steel in the photo?And that powdery looking stuff adjacent to that looks like Galvonic corrosion.

Not to mention he did a terrible job of controlling cleanliness prior to and during the paint application judging by all the solid inclusions in the paint(Looks like it was painted in a sand Storm).I'm guessing he didn't use prepsol or a tackrag or filtered his paint.

Another thing I can't help notice is there's more than a few chips and scrapes on that boats paint?What you'll find will happen is the chips get wet with  saltwater,the saltwater eventually works it's way under the paint chips edge and under,then the water slowly dries leaving behind the salt which will expand under the paint and there's your bubbling paint as it's lost all its adhesion with the aluminium.

If I where to fix that mess I would first determine if infact there is dissimilar metals around the fuel cap.I would repair those dents and hit the whole existing paintwork with 180 wet/dry feathering all edges/chips.spot spray any bare alloy with etch primer than hit the lot with 2 full coats of polyester.Rub back with 320 wet/dry then 800 wet/dry and hit it with 2-3 full coats of basecoat colour followed by 2 good coats of clear all in 2k of course.

That's what I would do if I wanted it fixed properly.

Otherwise you can spot repair and colour match blending into existing paintwork.

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Thanks Fab1 and Zoran

I'll have a read of those links later.

I agree that he did a crappy job.  He certainly talked a good game and is a professional smash repairer, but he did it for cash and obviously didn't care about the end result.  I was furious about it for a while but have moved on now and just want to get on with it.

There are quite a few scratches around the boat which is mostly because I have no qualms about bumping into trees/jetties/oyster leases when I'm out on the water.  It is a fishing boat after all and was never intended to win a beauty contest.

My concern with your suggestion Fab1 is that I know there are areas all over the hull, particularly inside the bow and on the outside of the transom that were rubbed back to bare metal before the respray, and they haven't been etched.  If I was to just leave that paint on now and do as you suggest, I'm worried that it might only be a matter of time before these issues crop up again.

I'm thinking maybe I should just deal with the patches now and clock up a few hundred more hours on the outboard and then upgrade to a new boat in a couple of years.

Oh and re the fuel filler.  It's all aluminium and held down with aluminium rivets.  The cap, I think, is chrome plated brass.  Never had corrosion issues in that area before the respray.  Again this is a part that was bare metal and not etched (or properly cleaned is my assumption).

 

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3 minutes ago, TK01 said:

Thanks Fab1 and Zoran

I'll have a read of those links later.

I agree that he did a crappy job.  He certainly talked a good game and is a professional smash repairer, but he did it for cash and obviously didn't care about the end result.  I was furious about it for a while but have moved on now and just want to get on with it.

There are quite a few scratches around the boat which is mostly because I have no qualms about bumping into trees/jetties/oyster leases when I'm out on the water.  It is a fishing boat after all and was never intended to win a beauty contest.

My concern with your suggestion Fab1 is that I know there are areas all over the hull, particularly inside the bow and on the outside of the transom that were rubbed back to bare metal before the respray, and they haven't been etched.  If I was to just leave that paint on now and do as you suggest, I'm worried that it might only be a matter of time before these issues crop up again.

I'm thinking maybe I should just deal with the patches now and clock up a few hundred more hours on the outboard and then upgrade to a new boat in a couple of years.

Oh and re the fuel filler.  It's all aluminium and held down with aluminium rivets.  The cap, I think, is chrome plated brass.  Never had corrosion issues in that area before the respray.  Again this is a part that was bare metal and not etched (or properly cleaned is my assumption).

 

If it hasn't been etched problems will arise in future.Like Zoran said,don't worry too much and go fishing until the time comes to sell.Then decide to either sell it as is or pretty it up with some spot repairs.Otherwise to fix it properly your looking at a full re-spray.

Good luck with it.

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I think the chromed brass cap is causing the problem with the filler.  Brass and  aluminum are the worst combo for electrolysis.  

I would clean filler back to bare metal, prime and paint then replace cap with plastic one.

Good luck. Ron

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16 hours ago, campr said:

I think the chromed brass cap is causing the problem with the filler.  Brass and  aluminum are the worst combo for electrolysis.  

I would clean filler back to bare metal, prime and paint then replace cap with plastic one.

Good luck. Ron

Thanks Ron, on a positive note that shouldn't be very difficult since most of the paint is falling off there already:D

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