clean rust pits?

[Jr. Roby]

Is muriatic acid ok to clean metal prior to primer?if so how to cut it?
 

[Stephen Newell]

Personally I prefer sand blasting however muriatic acid will clean rust off especially if brushed with a brass brush. The problem is it will quickly rust back if not treated. It should be cleaned off with oxalic acid or vinegar, rinsed and dried afterwards. Then as soon as you get the moisture off of it, it should be primed with epoxy primer. Any surfacing or bondo work can be applied over the epoxy primer.
 

[CNKS]

NO, not a good idea, HCl is too strong, musst be washed off within a few minutes of application, and you will then get flash rust. You will consider Picklex 20 expensive, but you will use very little on the sheet metal and it will do several tractors. It does not need to be washed off, read the info in the link.
Picklex 20

 

[showcrop]

You want phosphoric acid. Google it. It tells you about how it forms a protective film. You can get it at an auto parts store under many different names or spend 1/4 the money and get it at a dairy supply or restaurant supply where they sell it for removing mineral film. I spray it on, keep the part wet for 15 min, then rinse off well. I also use a bucket to dip small parts for 1/2 hour or so then rinse in a second bucket for ten min. It will get right down in the pits better than sandblasting to dissolve the rust.
 

[souNdguy]

yep.. naval jelly or other phos acid containing prep.

hint.. some driveway cleaners that remove rust in a gallon jug for 9$ at lowes contain phos acid and will eat that rust.. then rinse and get working on that metal.. etc..