vins0010

I'm working on a couple bikes this winter and would like to do rust removal. Traditionally, I put the frame in a weak oxalic acid bath, outside. Now, it is almost January in Minneapolis and I don't think that'll work. I'm very hesitant to do the weak bath indoors as everything says to have ventilation, which I don't really have much of in the basement. Is this a concern with a very weak bath? If so, any other ideas about what would work inside? I'd like to do some sort of bath if possible as that is very much easier than tackling each rust spot individually. Thanks.

pierce

the dust from the powder pure oxalic acid is quite hazardous to breath, but once mixed, its fairly dilute (1/8 cup per gallon of water), so I wouldn't think the fumes would be /too/ bad. of COURSE keep it way the heck away from any chlorine products. wear chemical grade rubber gloves, a splash shield for your face, etc etc.

pierce

can anyone here who's used oxalic acid on bike parts chime in? I've got an old all campy 1974-5 Motobecane Grand Record... all the chrome bits on the old campy parts and frame bindings are rusty, and I'd love to make them shiny again... what treatment would you put on this sort of thing AFTER you've done the oxalic bath and rinse so it doesn't get rusty again ?




also, do I need to remove aluminum bits, or is alloy OK in the oxalic bath?

hhuytho

This product works well: https://www.evapo-rust.com/

rydabent

A cheap bottle of CLR would probably do the job too.

wrk101

There are at least 500 threads on Oxalic Acid already, and yes, you need to remove anything that is aluminum. OA also attacks zinc coated spokes.

Try doing a complete frameset, say 30 to 40 gallons of solution, with evap-o-rust. Lets see, Evap-o-rust is $30 a gallon. Becomes cost prohibitive on larger jobs. Meanwhile, similar OA cost in a 30 gallon bath is about $3 if you buy OA in quantities, $20 if not. On small parts, I reuse the same solution for several months, treating parts at least weekly.

I do my OA treatment indoors in the winter, in the basement. Smaller jobs I just have a container in the workshop.

pierce

well, all the chrome bits on my old campy bike wouldn't take more than 2" in the bottom of a coffee can, I suspect. I'm pretty sure some of the bits have alloy stuff thats swaged on and not diassembable, so I'll likely go with evaporust if I ever undertake this project.

parts like that headset, and the shifter clamp, in that picture above... once I get all the rust off, what would you do to keep the bare metal from rusting up again where the chrome is gone ? just wipe them down in WD40 and keep them all a little oily? or some sort of wax? silver spray paint? send them off to be re-chromed?

Spld cyclist

You can use a vinegar solution for rust removal, as well as citric acid solution. Neither will cause hazardous fumes. I'm a fan of evaporust, but as someone said above, it's not cost-effective if you need to soak something large.

pierce

I don't quite get the chemistry behind using an acid... acids oxidize metals. iron oxide is rust.

Airburst

If my half-remembered chemistry is correct, in the right conditions, some acids can also act as reducing agents.

wrk101

Ferric oxide (rust) reacts with oxalic acid, forming ferric oxalate. It is not reacting with the steel, it reacts with the rust.

Other acids will also react with the rust, they are just more expensive and less effective. The choice is yours.


Good read from the BMX forum:

https://www.vintagebmx.com/community/...wtopic=4004702

pierce

so, my other question... after cleaning up badly rusted formerly chromed bits like that headset, shifter clamp, on my Motobecane... what do you suggest for protection on the now bare steel exposed between whatever chrome is left to keep it from getting all rusty again ?

Fred Smedley

1/8 cup per gallon of water? Seems pretty excessive given .02 % is around 1/4 cup in a eighty gallon kiddie pool and works just fine in around 30 hours @ 70-90 degrees.

pierce

ah, that 1/8 cup per gallon was what I read on several how-tos.

sigh, won't get to 70/80 degrees here until next summer, and then only during the days (pacific ocean cools things off to the 50s the minute the sun drops). we keep indoors at 66-67F and the garage is completely unheated and drafty.