 | Home > Maintenance & Modifications > Corrosion in rear tub |
 
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| LandRoverAnorak Member Since: 17 Jul 2011 Location: Surrey Posts: 11324  
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Electrolytic corrosion on ali usually takes the form of grey/white powder. Is it possible that something unpleasant has been spilled? Darren
110 USW BUILD THREAD - EXPEDITION TRAILER - 200tdi 90 BUILD THREAD - SANKEY TRAILER - IG@landroveranorak "You came in that thing? You're braver than I thought!" - Princess Leia |
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28th Jan 2020 12:13pm |
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| rustandoil Member Since: 08 Sep 2012 Location: Cotswolds Posts: 738  
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Probably not much help but my 2005 Doublecab has suffered the same fate
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28th Jan 2020 12:28pm |
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| lonewolf Member Since: 23 Oct 2013 Location: North East England Posts: 210 
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LRA.....no, nothing spilled in there, it’s normally quite clean and if there is any debris it always gets dealt with pronto.
Eddie, have you done anything to sort it out or know a solution? I knew I’d not be the only one. Lots of people soundproof theirs, so how would they know if they had similar issues. TBH I think it will have something to do with electrolytic corrosion but the greasy substance has me stumped. I sprayed the affected areas with acf50, in the hope that it would help? |
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28th Jan 2020 12:56pm |
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| rustandoil Member Since: 08 Sep 2012 Location: Cotswolds Posts: 738
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 Click image to enlarge Mine has turned into a complete rear floor and rear "seatbox" rebuild...lots of new metal to go in... My job started with the rear body crossmember, common rot point on 110 SW and DC and went from there..  |
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28th Jan 2020 1:17pm |
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| lonewolf Member Since: 23 Oct 2013 Location: North East England Posts: 210
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Nightmare
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28th Jan 2020 2:23pm |
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| Supacat Member Since: 16 Oct 2012 Location: West Yorkshire Posts: 11018 
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Photos would be good but it does sound like the dreaded electrolytic corrosion, if water is also present it will form a paste.
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28th Jan 2020 6:22pm |
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| lonewolf Member Since: 23 Oct 2013 Location: North East England Posts: 210
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Supacat......I’ve wiped all of the pasty stuff off so no photos, but if I find anymore I’ll post a picture. This is irksome as my 90 is well looked after. I’ve read up on the science behind this and it’s all to do with the nobility of metals in contact with each other which then gives local corrosion spots. My 90 is showing signs of these spots in a few places not necessarily near to each other which makes me wonder if say a bad earth or whatever could be exacerbating the corrosion. I’m no expert so may be well off the mark here. Frustrating to say the least!
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29th Jan 2020 10:23am |
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| rustandoil Member Since: 08 Sep 2012 Location: Cotswolds Posts: 738
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Another place to check is where the front seatbelts attach to the sill...
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29th Jan 2020 11:41am |
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| lonewolf Member Since: 23 Oct 2013 Location: North East England Posts: 210
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I’ve just been outside grinding the corrosion out. Only 3 places, but from what I can see where the rear tub alloy is in close proximity to the steel of the chassis member, (the places you can see underneath that has the vertical lipped rectangular cut outs with the rounded corners). One of the holes is just near one of the radiused corners.
Seems to me that the alloy of the tub has been perhaps in contact with the steel (perhaps rubbed and removed any paint over time) and setting up the electrolytic corrosion. For now I’ve body filled the holes so I’m not getting water sprayed in and will see how it goes. Although the underside is waxoyled the areas where the rectangular cut outs are are great traps for water and mud to get into. I keep the underside of mine quite clean by pressure washing with water only. Also I think it’s worth mentioning the steel brackets for the rear seats are near the holed areas in all cases which seems a coincidence. These brackets are not isolated from the alloy tub apart from a painted surface. Back in the house now trying to get warm as it’s bloody freezing outside. I’ll be checking out the seat belt brackets in due course......cheers  |
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29th Jan 2020 2:09pm |
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| Scotm Member Since: 28 Feb 2014 Location: Aberdeenshire Posts: 666  
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I would be stripping the seats out and getting it all treated. The holes can be patched with aluminium plates. Best to isolate the seat brackets with plastic before putting back together.
My have my rear seats in and out over the year and have spotted the odd electrolytic corrosion starting around some of the bolts. I make sure they are soaked in ACF-50 to prevent this. |
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29th Jan 2020 2:14pm |
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| lonewolf Member Since: 23 Oct 2013 Location: North East England Posts: 210
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^^^
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29th Jan 2020 3:43pm |
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| lonewolf Member Since: 23 Oct 2013 Location: North East England Posts: 210
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Update.....more of these little holes appearing with the pasty stuff. It’s definitely associated with galvanic corrosion. I’ve come to terms with it now (what will be will be) and will be removing rear seats when the weather gets warmer, drilling out the spots and filling the holes. The interesting thing is that if I get a hole on one side there is a similar hole on the other side of the tub in the same place a bit like how you get matched hair on your beard on either side of your face, that’s the best way I can explain it. Quite intriguing really. I have introduced a few stainless bolts to the vehicle but not that many and always use Ducolac on them before fitting them but these little holes aren’t anywhere near to them. If any areas need it I’ll be patching over with new aluminium riveted but not near that stage yet. As I’ve said before though if the rear tub had been covered in soundproofing I wouldn’t have been aware of the corrosion being present. Apparently you can wash these areas with a solution of soda crystals to negate the galvanic process. Looks like a job for the summer months. It’ll keep me out of mischief I suppose.
Bottom line is the Defender still makes me happy.......ish.....£570 tax to pay at the end of this month.......aargh! |
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22nd Feb 2020 8:48pm |
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| Grouse Member Since: 16 Apr 2012 Location: on the hill Posts: 520 |
I had exactly this with a Series 3, 36 years ago, just a rubber mat in the rear load bay with damp trapped underneath caused it - no other metal in contact - small patches with seal and and pop rivets cured it
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22nd Feb 2020 9:35pm |
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| Dinnu Member Since: 24 Dec 2019 Location: Lija Posts: 3414  
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Recently got a 90 CSW and first thing i noticed is how much steel is in contact with aluminium on the rear tub. Inside the wheel arch, the tub is reinforced with steel. This is riveted with steel rivets at various places, plus all the bolts for seat brackets and seat belt anchors. It is designed to trap water and mud between the alu and the steel. On mine, the supports from rear seat belt mounts to rear crossmember looked horrible, luckily all surface rust. These are first to attend to hot dip galvanizing. I plan to take out these steel reinforcements, not yet decided if they will get hot dipped galvanized, or just a good clean up and proper etch prime and paint. Definitely will put in some isolation between the metals. Some parts of paint applied at factory has came off from the steel reinforcing on the first steam wash.
Front seat belt brackets to chassis have exactly the same issue. They just hide out of sight. 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing 2012 90 CSW, 2.2TDCI, Santorini Black |
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22nd Feb 2020 9:50pm |
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