Alum for galvanic seize

Discussion in 'Bicycle Repair' started by FurryOnTheInside, Sep 26, 2016.

  1. FurryOnTheInside

    FurryOnTheInside Well-Known Member

    Inspired by @butre 's post over on the broken bolt thread, I wonder if dissolving the pedal spindle thread with a bath of heated alum would leave my aluminium crank arm's thread usable again?

    All the bicycle forums I have searched seem to come up with the same thing- pb blaster & a huge lever.
    Might be fine if it was just overtightened or dry, but I live right by the sea, bought the used bike locally, and I just know that these pedals are galvanised to the crank arms, and that this method will tear the aluminium threads from the crank arm.

    As a method for a mount stud on an engine, tearing out threads may be okay because the hole can be drilled out and rethreaded to the next size up; but unlike studs, pedals only come in one size.

    So does soaking in heated alum present a viable alternative for those who bought a used bike and want to upgrade the pedals?

  2. zippinaround

    zippinaround Active Member

    bit of heat should do the trick just heat it a bit leave it to cool then take the pedal off , but i can say i removed pedals from my 1985 raleigh maverick , i just removed the crank arm and left the pedal to soak in oil after i wire brushed the backs, came right off the next morning with no thread damage.
  3. FurryOnTheInside

    FurryOnTheInside Well-Known Member

    I don't actually have heat, apart from my oven lol. I could buy a propane blowtorch but now I really think that the steel is chemically bonded to the aluminium. I have tried soaking in penetrating oil, gentle heat going from freezer to oven, and lots of force with a short lever. I hoped that would be enough to get it un seized but I didn't want to use a big lever because anything that well stuck on must be galvanically bonded. I could be wrong but I don't dare risk it! I don't mind losing the pedals so the alum seems like a possibly great solution.
  4. zippinaround

    zippinaround Active Member

    yeah it should work , if you have tried everything else already it looks like you have no option really , if you have a welder could try welding the pedal to redden it ?
  5. FurryOnTheInside

    FurryOnTheInside Well-Known Member

    No, I've no way of heating up the crank arms (and it would need to be primarily the arms, not the pedal spindles) quickly so as to take advantage of the faster rate of heat absorption and expansion of the alloy over the steel. I don't think it is the right kind of seized for this to work, anyway, just because I have used enough force to make me think that any more would simply tear the aluminium threads. In the circumstances, being right on the coast, I'm going to assume it is a chemical bond. That's got me wondering what the outcome of using this chemical reaction to free the pedal would be.
    I think unless I hear that it won't work, I probably will be having a go at this method, as soon as I start seeing aluminium turkey roasting pans in the supermarkets again. :)
    zippinaround likes this.