japheth

I bought an old radac rd-570 frame. These were japan surplus so most of them were relatively well kept. What I was not counting on was an over-tightened kickstand. it bit through the paint and from there it was a non stop train to rustville. I thought maybe it was just some surface rust but there's some serious pitting. I've grinded off the worst but I really don't want to end up taking off too much material. I really can't tell how bad it is. while it doesn't appear to have eaten through I'm worried about those tiny pitting all around the seatstay and chainstay. Some additional eyes would help. I'm not attached to this frame but I don't wanna throw it away if I don't have to.

SkyDog75

DON'T GRIND. If you do, you're removing steel from a tube whose walls may be less than a millimeter thick. (Some steel tubing used for bicycles is as thin as 0.3 millimeters!) There are chemical methods to remove rust that don't remove any metal, such as a cheap & easy oxalic acid bath. Added bonus: an acid bath removes rust from inside the frame, too. An acid bath won't remove pitting, but you can fill pits those when prepping for paint.

jimc101

Too late

japheth

yup. was only supposed to take off the paint. Wasn't paying attention and wasn't wearing my glasses and ended up using 200 grit instead of the 2000. Good thing Though the end seat stays on this thing are pretty thick, around .8 - .9 mm so i don't think I effed up too badly. Tying that oxalic acid bath right now.

02Giant 

I think the definition of "grinding" is quite different from the OP to the later posters.

Glasses or not, you should be able to feel the difference between 200 and 2k grit.

dsbrantjr

They don't remove any additional metal; what has turned to rust is gone for good.

Spaghetti Legs 

That is negligible rust that I can see. You were a little aggressive with that chain stay however. Get some Loctite Naval Jelly or Evapo Rust to take care of any rust spots. Naval jelly is cheaper and works better for little spots.

Kozeemoto

Unfortunately for those that experience such a thing it is much worse that surface rust on a true steel bike. The Radac rd-5** were a hybrid of aluminum main frame/triangle with steel stays and fork. The problem this creates in a moist environment is due to electrolysis, or what is called galvanic corrosion. Usually zinc coating inside and out can prevent this for some time as the zinc becomes sacrificial but eventually the phenomenon prevails. In the case of the radac it seems as the steel suffered more than the al-alloy, which may be due to what the alloy was made from.

San Rensho 

Or phosphoric acid. A little less aggressive than oxalic,

Kimmo

And I was nearly the guy to ask the OP of this three year old thread to post a pic of the whole frame