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  1. #1
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    Removing NaOH from inside the frame

    So I got a used steel frame and it came with a completely seized Al alloy seat post.
    I dissolved this out (during the recent cold snap here) and as best I could washed out the insides and then dried and added WD40 until the insides were dry before reassembly. Washing out was hit and miss due to sub freezing temps… (no hosepipe)
    Anyway, rebuilt quickly but now I’m getting NaOH coming out when I get water in the frame .
    Essentially it must have recrystalised in the colder sections inside the frame (like chain stays) and now its coming out in bits...

    Obviously not the best for HSE … but worse I’m worried its going to drop onto alloy components …
    I stripped it and washed it out again last weekend… dried and WD40…. squirted water in under pressure from garden hose against the drain holes in the seat stays and put a few gallons through the head tube and BB… until it started to run clean.
    I’m thinking of re-flushing again before assembly… but anything better than boiling water ??? (and obviously not something that is bad for CrMo…. )
    I could flush it with an acid but H2SO4 or even HCl might not be great for the steel…. and I have a fairly limited supply of these anyway… and I can probably no longer even buy more of the sulphuric (one shot)….

  2. #2
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    I've used an oxalic acid bath to clean a steel frame and get rid of rust and simply rinsed it out well after. Then after drying used this stuff called framesaver to spray inside the frame to protect it.

  3. #3
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    Quote Originally Posted by dundundata View Post
    I've used an oxalic acid bath to clean a steel frame and get rid of rust and simply rinsed it out well after. Then after drying used this stuff called framesaver to spray inside the frame to protect it.
    Thanks ... I used some boiling water then a few gallons from the hose but still not sure I cleared it out ... I think it’s probably a mix of NaOH and aluminium oxides and the oxides are pretty insoluble

    The frame saver sounds good .. I’ll check that out !!

    I just rebuilt the frame but I’ll maybe see how it goes for a week and check back ...

  4. #4
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    Being that Sodium Hydroxide has such high pH you will need to either neutralize it or use hot water to get it out. If not there will always be a residual. If you want to use acid I would use Acetic acid or white vinegar diluted with water. The vinegar will not do harm to the steel frame, if anything it would help remove rust and scale from the inside. A better way would be Citric or Oxalic acid diluted along with Dow Versene (EDTA) but few people have this just lying around. After either one and it has dried you will need to put some kind of penetrating oil or rust preventative.

  5. #5
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    Thanks firebrand
    I’d probably find citric acid or oxalic pre-mixed with a chelating agent in industrial descalers?

  6. #6
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    If you cant find Framesaver, LPS 3 is a similar alternative that you should be able to find at hardware stores. In my short term testing with pieces of steel bike tubes in seawater they performed the same.

  7. #7
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    Quote Originally Posted by Steve-XtC View Post
    Thanks firebrand
    I’d probably find citric acid or oxalic pre-mixed with a chelating agent in industrial descalers?
    Yeah I am sure there are commercial descaler/chelators on the market. Most of the time though they keep their formulas as "proprietary" so they do not tell you for sure what they are or concentrations. MSDS will give you a clue to point. I keep the stuff because we mix it to the specific projects we using it for. If you need something, IM me.

  8. #8
    RAKC Industries
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    Good info on cleaning but long term solution has been missed.

    Your dealing with galvanic corrosion. Aluminum and steel in contact with each other in corrosive environments dont mix well. Need to use an anti corrosive lube/grease or go straight to anti-seize once things are cleaned out and you reassemble. Will avoid this problem in the future which can quickly corrode both the frame and the seat post.

    Sent from my SM-G950U using Tapatalk
    Life on a bike doesn't begin till the sun goes down.


  9. #9
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    Quote Originally Posted by firebike7 View Post
    Yeah I am sure there are commercial descaler/chelators on the market. Most of the time though they keep their formulas as "proprietary" so they do not tell you for sure what they are or concentrations. MSDS will give you a clue to point. I keep the stuff because we mix it to the specific projects we using it for. If you need something, IM me.
    Thanks, I'm in the UK so that would make it difficult but thanks for the offer.
    Now I'm actually thinking about this (due to the stimulating answers on here) ... I'm more convinced the problem is either partly or largely due to the aluminium oxides being mixed in with the NaOH.

    That was probably compounded by trying to do this outside in sub zero temperatures... that led to both a very rapid cooling of the solution and lack of a hosepipe to flush....

  10. #10
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    Quote Originally Posted by RAKC Ind View Post
    Good info on cleaning but long term solution has been missed.

    Your dealing with galvanic corrosion. Aluminum and steel in contact with each other in corrosive environments dont mix well. Need to use an anti corrosive lube/grease or go straight to anti-seize once things are cleaned out and you reassemble. Will avoid this problem in the future which can quickly corrode both the frame and the seat post.

    Sent from my SM-G950U using Tapatalk
    The galvanic corrosion occurred due to the previous frame/bike owner sticking in a aluminium alloy seat post without grease and not moving it for 5 years.
    The current seat post has a liberal coating of PM600 and also gets raised and lowered frequently.

    To be honest I don't think they actually used the bike much in the 6yrs or so since purchase so for me it was a bargain... the whole bike cost less than 3 decent tires... then of course I had to replace the seat post... but the "purpose" of this bike was a cheap aggressive hard tail to hack about... (the cheap is as much for the family financial controller) ...

    The good news is I took it out this weekend ... (along with a "proper bike") to a UK bike park with some DH, some dirt jumps, pump track etc.
    When I say "proper bike" my trail bike usually has a lot less travel than anything else on the uplift anyway (140/130)... but I decided to give the steel HT a play on the mildest DH and it was going great until I had pinch flat... (it's even got tubes..how old-skool cute is that but I'm running a rear tire a friend gave me as it got wrecked for ever running tubeless)

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