Question:

Why is my frame flash rusting in seconds?

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I am restoring a motorcycle. The frame is mild steel. I have sandblasted it with coal slag, as recommended by the supplier after personally inspecting my frame. My blast booth was partially damaged by a storm last week, and some rainwater hit the blasted frame, causing it to rust overnight. I didn't want to take the time to fix the booth so I could blast it again, so I treated it with The Works - Calcium, Lime, and Rust remover (basic household cleaner; oxalic and sulfamic acids). I diluted it about 15:1, sprayed it on, and washed it off with water. I've done this sort of thing before without any problems.

But it rusts before it dries in direct sunlight in 95 degree weather in the desert. Two to three minutes tops.

I tried again, drying it with compressed air, and it still rusts though not as much.

I bought Naval Jelly (phosphoric acid) and used it per the instructions. It says to prime within 24 hours to prevent flash rusting. But it rusts within minutes.

I finally just blasted it again, and it's now rusting again without any moisture. (I live in the desert. There is no moisture in the air.) It actually rusts before I finish blasting.

I don't understand what's happening, and I can't prime it until I get the abrasive dust off. The shape is far too irregular for hand sanding to be realistic, and even then I still have to wash off the dust somehow without creating more rust.

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3 ANSWERS


  1. I can only guess, cause this isn't my specialty.

    Perhaps the frame is porous.

    The blasting material absorbed some moisture - your process of removing the moisture wasn't adequate.

    When blasting the frame, moisture is getting into the metal.

    Perhaps if you put some humidity absorbent packs in the blaster cabinet, that would cure your problem.

    http://www.drypackaging.com/

    This stuff is available at hardware stores.


  2. wipe it with pre-cleano

  3. sounds like you don't have a drier or water trap in your air supply line or its not working.

    have you drained your compressor tank lately?

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