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Severe aluminum shaft log corrosion/deterioration

Discussion in 'Technical Discussion' started by Scallywag, Jul 22, 2012.

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  1. Chevelle

    Chevelle New Member

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    "Wow! Amazing those props even turned with that kind of damage! Glad you got everything resolved thought. Were there bronze set screws in the cutlass bearings by any chance? Any clue what caused your corrosion?

    I'm having an epoxy barrier coat put down under the stuffing boxes and in the shaft pump well to address some of the pitting that is occurring. Did you run into any similar issues with your Broward?"

    To edit my post, we cut 6 INCHES not feet off the forward end. there was quite a bit of plate corrosion in the "well" below the shafts. This area had resin of some sort poured into it to try and get water to flow forward to the engine room through conduit that the water cooling hoses ran thru. That made no sense, the hull was lower than the conduit, so they poured goop in there to raise the "floor". Needless to say, lots of corrosion from salt water getting under the "resin" and an incredible stink that the owners had complained about for years!

    We replaced the old Aluminum stuffing boxes with lasdrops, put a shortened cutlass bearing in that end of the log and used Belzona to seal up and protect the plating. We also replaced the remaining Cutlass bearings and of course reshot (laser) and chalkfasted the whole thing. It took a lot of time to get the alingment right as it was off by huge amounts. Ended up having to move the Engines a bit, replace rusted through motor mounts and custom build a new tranny mount bracket after one was found to be Broken!

    Years of Neglected are the answer to how this happened. My friend took over the boat a few months ago and started digging. The owners had the boat built in 1988! had to replace some hull plating in the ER due to metal and dirt in the bilge, hiding under "drip pans"! All in all we tore a Ton of stuff apart and it is a better boat for it.

    Now most importantly, everything that everyone has posted about the welds is correct, those are horrible. The logs do not look like they were cleaned at all. Do it over!!!!!!
  2. Scallywag

    Scallywag Member

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    Thanks for the input guys. The welder doing the work has been welding around here for more than 30 years, has a good reputation, and came highly recommended. He mostly welds on work boats and has replated hulls and done work on Coast Guard boats.

    The welds were MIG welded with 100% argon. Your comments prompted me to call in another welder for advice. I didn't tell him who did the work or any other details to avoid conflict of interest. I had him look at the welds and let me know his professional opinion.

    He said the welds don't look cold and penetration looks good from both sides. He agreed they are ugly, but felt they were structurally good. He explained he personally would have used a TIG for a nicer finish and that "stacking dimes" look you see on tuna towers and the soot from the MIG weld is unavoidable.
  3. wdrzal

    wdrzal Senior Member

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    Thats just plain BS, you spool out new clean aluminum wire and it's covered by a argon gas shield. Where would the soot come from???? MIG or TIG with argon gas will leave the plate as shiny as it was before welding................In your case the surface wasn't prepared and cleaned correctly, thats where the soot came from.

    It should look like the pics Bill106 posted.

    Walt
  4. K1W1

    K1W1 Senior Member

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    Hi,

    I agree with the previous comments about the appearance of the welds.

    The area should be ground as it appears to have been and the wire brushed with a SS wire brush, sometimes some solvents or something left from the initial treatment seem to cause weld problems.

    If your "independent" expert says they look good, I would call into question his abilities.

    For definitive proof of the welds integrity have them x rayed before you get the tanks pressure tested.

    Basically the ones outside look like cold overlay, poor penetration and dirty surfaces to me.
  5. Scallywag

    Scallywag Member

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    Bills pics look absolutely excellent. Was that accomplished with MIG? In a shop or a yard? Upside down? Wind conditions?

    Turns out a guy at the yard that I've shot the breeze with just about every day for the last three weeks welds. He just about mirrored exactly what the other welder said.

    I know close to nothing about welding, but it seems like everybody here concurs that if it isn't a roll of dimes it's a bad weld and if there is soot then the weld is cold and penetration is bad. Every professional I've spoke to says otherwise when they have nothing to gain either way?

    I guess keep asking different professionals for consultation until I find one that agrees?
  6. Scallywag

    Scallywag Member

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    And contaminate the alloy with stainless steel???????
  7. K1W1

    K1W1 Senior Member

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    Hi,

    I have sent Photo 1 from Post 17 to a couple of guys I know who between them have more welding experience than most will accrue in a lifetime.

    One is an ABS Senior Surveyor, the other a welding superintendent in a major shipyard.

    I will post back with the opinions
  8. Scallywag

    Scallywag Member

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    That is excellent Kiwi! Thank you.
  9. Scallywag

    Scallywag Member

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    Got it. That makes much more sense. The phone pictures don't help.

    There is about 12 inches of shaft log tube inside the hull, but the weld is "built up" a bit under the tube leaving about 8 inches. Enough for a bunch of hose clamps.
  10. Marmot

    Marmot Senior Member

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    Just read today's posts ... geez, that really is an ugly bunch of welds! It looks like something I might have done while trying out a new spool gun.

    That soot is from using 5xxx series wire and dragging the torch rather than pushing it. Some of that soot will be included in the weld itself and lead to porosity. A little bit of soot is all but unavoidable because it is from the magnesium in the metal. If you use a wire brush on a die grinder it will actually combust and make a neat looking expanding ring of orange that looks like a grass fire as seen from the air.

    I guess if you slobber enough metal on something you might get structural support but usually a weld is about as good as it looks and those look like crap, not matter what the locals say about it.
  11. Capt Ralph

    Capt Ralph Senior Member

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    Then that should be plenty. I with draw my concern on that then.
  12. rgsuspsa

    rgsuspsa Member

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    The weld photographs depict weld regions which appear sound, and regions which appear quite poor. For any given weld joint the entire weld, both internal and external to the hull must be sound. I believe these welds are going to be problematic within a period of time which will be quite short of their intended service life. Either deal with them now, or someone will be dealing with them in the not too distant future.
  13. Scallywag

    Scallywag Member

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    Thanks for chiming in Ron. The collective knowledge of this forum is amazing. I've done quite a bit of reading over the past week regarding welding and have learned quite a bit. As always, I still have tons to learn.

    The in the Weld Defects section of the MIG handbook it refers to porosity. As I understand it, the soot is indicative of porosity usually caused by unclean material or inadequate shield gas. With MIG welding it is often caused by "dragging" the weld instead of "pushing" it. Especially with 5000 series wire. The porosity may or may not be inside the joint, but the only way to tell is by x-ray. In practice, excessive sooting is a good indicator of porosity.

    Let me know if I have that info right.

    A lot of this has been stated in different ways by forum members. What amazes me is the "professionals" haven't mentioned this even if they have nothing to lose by saying "that there weld is a pile of crap!"

    I appreciate everybody's input and hopefully I can return the information overload I'm receiving to the next new member.

    Starboard side is removed and ready for welding. The outside weld is the most concerning to me. The inside hull welds seem adequate. As was stated by somebody else "grind it out and do it again!"

    Attached Files:

  14. Savasa

    Savasa Senior Member

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    Scallywag,
    I'm no welder but there is NO penetration in the tube in the last pictures you posted.
    Peter
  15. Scallywag

    Scallywag Member

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  16. Bill106

    Bill106 Senior Member

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    That was definitely MIG and inside the shop with no wind to blow the gas away from the weld. Some were inverted and just about any orientation but I couldn't tell a difference. I am by no means an expert in welding but those guys we hired are the absolute best I've ever had the pleasure of working with. There is a huge difference in tower stick welding (TIG) and plate welding and I've got a renowned tower builder across the street but when these guys were at work they came over and stood slack jawed at the artistry being created. One of the guys had over 25 years of aluminum hull building experience but his apprentice was nearly as good after only tweo years.

    The second set of pics you posted up looks much better to my untrained eye
    and mainly because the start/stops looked properly done. One thing those OA/SWS guys taught us was the proper way to do that was to grind back into the end of the weld before restarting.

    Be leery of soliciting advice from general purpose welders. I've discovered there is a specialty within a specialty when it comes to proper metal hull building techniques.
  17. Marmot

    Marmot Senior Member

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    Try the professionals at Miller, they might not agree with the ones you have spoken to. Or, if you like, go take a look at an aluminum boat built by Derecktor or any another builder with a reputation for quality aluminum boat building.

    AL MIG welds from Miller:

    Attached Files:

  18. ArielM

    ArielM Senior Member

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    I am not a professional welder but i enjoy metal fabrication on the side and the welds done on this repair are not adequate at all.

    First of all a repair like this should be TIG welded by a professional. Due to the fact that this hull have been sitting in salt water for this long, there is a lot of oxidation and contamination in the base metal. Welding alum. is very techincal and should only be done by a professional. There is also no cleaning action around the foot of the welds. weld is also too cold. You should also check what filler metal the welder used. 5356 (or 5xxx series) is marine grade alum.

    Lack of "stack of dimes" DOES NOT mean it is a bad weld. the stack of dimes comes when you add filler metal to the weld puddle. If the welder feeds filler metal at a faster pace or lays wire then the ripples come much closer together and you can lose that affect without sacrificing the joint.

    I wouldn't trust those welds one bit.

    On a side note cleaning the alum with Stainless Steel brush is common practice. (That brush should not be used on any other metal though)
  19. H4M

    H4M Guest

    I've seen better welds but I'm not a weld expert, however we have had recent experience on bearings installed in Al ships, there had been problems with previous shaft bearings where corrosion was seen between the bearing and the bearing carrier/tube/strut. This caused some bore closure and tight running which gave shaft and bearing wear. These were composites that were freeze fit so no metal to metal issues just pockets of salt water. These were changed for clearance fit fully composite phenolic bearings these from Australia were also resistant to marine growth, so far (three years) so good, very low wear rates and no shaft damage or corossion. So epoxy bedding to manufacturers clearances seems to work well.