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Thread: Corrosion Pitting repair

  1. #1

    Corrosion Pitting repair

    My 22y/o Quintrex has severe pitting in the hull down at the transom. I knew there was some evidence when i bought it 8 years ago, and kept it as clean as possible, and always flooding the hull after each salt water trip. well, finally 2 holes have appeared, approx 1/8", which obviously need welding. is there a chemical available that will dissolve the rest of the corrosion, so i can treat it to stop it advancing any further?

  2. #2

    Re: Corrosion Pitting repair

    You might be able to clean any corrosion off with a scourer, then etch it, then maybe paint to protect further, chances are, once you start digging you will find more holes.

  3. #3

    Re: Corrosion Pitting repair

    You can use a stainless wire brush on the grinder than try those new modern low temp melting aluminium rods i think there called HTS 1000 OR 2000 once u melt the rod on clean it up with the grinder and paint

  4. #4

    Re: Corrosion Pitting repair

    Those miracle welding rods are near impossible to use in any position but down hand, it is only a kind of semi controlled "melt" not true welding.

  5. #5

    Re: Corrosion Pitting repair

    Yeah i agree Noel i bought the wonder rods about 8 years ago when they first hit the market, i got mine from ebay they were shipped by a guy in Orange NSW i cant remember the brand name but yeah they were hard to use but what i did get to stick did work, i tried them again before i bought my big air compresser about 2 years ago so weld up a crack in a copper compressor pipe just couldnt get it yo stick, those rodsare suppose to work for a range of materials ally, copper, brass etc..

    Maybe eric can try low temp brazing using flux and a rod that is corrosion resistent than paint over the repair?

    Better option would be to have it welded i had my yammie 50 head welded for $300 if your in sydney eric go see the bloke all aluminium welding chipping norton

    https://ibb.co/ZSPS2pY

  6. #6

    Re: Corrosion Pitting repair

    I saw a ally boat pinholes repaired with JB Marine weld epoxy. The repair seemed to be holding up well and the colour of the cured epoxy was close to the ally colour. It was a pro boat so it got used often.

  7. #7

    Re: Corrosion Pitting repair

    Quote Originally Posted by BillB View Post
    I saw a ally boat pinholes repaired with JB Marine weld epoxy. The repair seemed to be holding up well and the colour of the cured epoxy was close to the ally colour. It was a pro boat so it got used often.
    That works although the last tube I bought was almost black in colour, probably picked up the wrong tube, what I've done is just use a blind ally rivet and dab a bit of silicone afterwards. Simple, cheap, quick to do. I'd reckon there might be more down the track though so time to sell snd upgrade.

  8. #8

    Re: Corrosion Pitting repair

    I'll try and put some pics up tomorrow. On closer inspection, there are dozens of corrosion pits forming, which eventually will rot through. Some are quite deep, so i doubt a wire brush or wheel will dig out all the salt. I can only think some sort of media blasting will clean it properly!
    wonder if something like alibrite would dissolve it?

  9. #9

    Re: Corrosion Pitting repair

    Are u sure u dont have a negative wire somewhere screwed down to the hull creating electrolysis? Aluminium doesnt just pit unless its been wet and dried a lot and alot of times over

    A mate bought a boat that was on its way to being a 25k write off he bought it with electrolysis and i told him we had to work out fast what was happening

    The previous owner had placed a off,1,2 battery switch connecting both positive cables to the switch but both negative cables were joint together and earthed to the hull it started to rot the whole hull

  10. #10
    Ausfish Platinum Member
    Join Date
    Mar 2015
    Location
    Kalbarri, WA

    Re: Corrosion Pitting repair

    This sort of thing is very common in the pressed ali hulls. Usually down towards the back where the water collects. It comes from letting saltwater dry out, the salt just starts to eat through. get a bit more saltwater in there, let that dry, you are just making the salt stronger and stronger. Happened all the time with our pro dinghys. Once it's started, no stopping it. You can slow it down by rinsing well with fresh water, but the damage is done. No chemical, or stuff like ali brite will make any difference. Almost impossible to weld, once the bits get close together. Wire brushing does nothing, you have to drill the pitting out and weld the resulting holes, but there always seems to be more salt and oxide there to stuff things up. Worst is when it happens along the join where the extrusion used for the keel meets the sheets--gets in there, just throw the boat away.

    How to fix it? we just used silastic, after wire brushing, sikaflex would be better. I've also done it with that Knead-it putty, that stuff sticks like the proverbial . Always keep some in the toolbox, I've fixed a plate ali hull with it once at least 10 years ago, that repair is still holding; he'd have to cut the deck out to get to it, so it stays.

  11. #11

    Re: Corrosion Pitting repair

    Quote Originally Posted by gazza2006au View Post
    Are u sure u dont have a negative wire somewhere screwed down to the hull creating electrolysis? Aluminium doesnt just pit unless its been wet and dried a lot and alot of times over

    A mate bought a boat that was on its way to being a 25k write off he bought it with electrolysis and i told him we had to work out fast what was happening

    The previous owner had placed a off,1,2 battery switch connecting both positive cables to the switch but both negative cables were joint together and earthed to the hull it started to rot the whole hull
    Ranmar's reply below is exactly how and where my issue is. i do have a 1/2 isolator switch, must confirm the neg isn't attached the hull. either way, the damage is done!

  12. #12

    Re: Corrosion Pitting repair

    Quote Originally Posted by ranmar850 View Post
    This sort of thing is very common in the pressed ali hulls. Usually down towards the back where the water collects. It comes from letting saltwater dry out, the salt just starts to eat through. get a bit more saltwater in there, let that dry, you are just making the salt stronger and stronger. Happened all the time with our pro dinghys. Once it's started, no stopping it. You can slow it down by rinsing well with fresh water, but the damage is done. No chemical, or stuff like ali brite will make any difference. Almost impossible to weld, once the bits get close together. Wire brushing does nothing, you have to drill the pitting out and weld the resulting holes, but there always seems to be more salt and oxide there to stuff things up. Worst is when it happens along the join where the extrusion used for the keel meets the sheets--gets in there, just throw the boat away.
    How to fix it? we just used silastic, after wire brushing, sikaflex would be better. I've also done it with that Knead-it putty, that stuff sticks like the proverbial . Always keep some in the toolbox, I've fixed a plate ali hull with it once at least 10 years ago, that repair is still holding; he'd have to cut the deck out to get to it, so it stays.
    this is exactly my boat, from the transom to the first rib. It was allready evident when i bought it, and as you mentioned, once it starts, you can't stop, even with a 50l fresh water bath after use. And yes, i'd have to cut the boat apart to get proper access!

  13. #13

    Re: Corrosion Pitting repair

    20210119_121008.jpg20210119_143600.jpg20210119_155822.jpg

    the damage done!
    looking at the pictures, i can see the damage is worse than what i can actually see!

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