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In this Instructable, I will show you one other way of prepping your metal for paint or powder coating.

Sandblasting is not always available. And other times you may not want grind marks to be visible. Pickling can be a nasty process and not always feasible for small projects.

This technique will get through the mill scale and rust, leaving you a nice finish that is ready for paint, powdercoat, or welding.

Here, I am using hot rolled mild steel 1/8" thick angle iron.

I did this at TechShop.

Step 1: Gather Materials

For this, you'll need the following:

  • Klean-Strip Prep & Etch, available at Home Depot (not at Lowe's)
  • A sanding block. I use a coarse 60 grit block.
  • Rubber gloves and safety glasses

The Prep & Etch comes in a big container so I got a spray bottle at Home Depot to make application easier.

Be sure to wear safety glasses and gloves when handling it.
 

Step 2: Spray With Etcher

Using a spray bottle, spray the etcher on the material. Cover all the surfaces with it.

Let it sit for 10-15 minutes.

Step 3: Sand

Now you need a little bit of elbow grease. Using your sanding block, make long smooth motions along the metal. The mill scale will slowly start to be removed.

Continue to apply etcher to wet the surface as you sand.

Step 4: All Done!

That's it! Now paint will adhere much better to the surface. It's actually a pretty cool texture if you would like to just leave it as is and apply a clear coat.

<p>very helpful </p>
<p>Does the acid also &quot;convert&quot; rust? I see some blackened pitting on the piece, but I can't tell if it's remaining mill scale on an imperfect surface, or if it's converted rust that would be safe to paint. </p>
<p>if you're looking to make a paintable surface just use ospho. it works great. </p>
wire wheel?
<p>I've tried a wire wheel but it doesn't seem to get through the mill scale very well. Also, I did not want swirl marks visible, which is the same reason I did not use a flap disc.</p>
<p>I assume step 3.5 would be to wash the etching solution off? </p>
Thank you!!!
I clean steel for etching or just to paint quite a bit. I found that Orange Clean, the hand cleaner, works well and it is cheap and environmentally safe.
<p>I'll have to try that. Thank you for the suggestion.</p>
<p>I would make one augmentation to your instructable, not to spray your metal on a stainless steel kitchen sink. Sure, one application probably won't hurt the steel, but since the solution you're using is essentially something like 40% phosphoric acid it will, with repeated application, start eating at the sink. If you have any scratches already in the sink it will start corroding those areas quicker. Do it in a plastic tub would be my suggestion.<br><br>This is, by the way, very similar to the method of cleaning steel with muriatic acid, something which is very common especially in industry applications. Phosphoric acid is of course more safe for home application.</p>
<p>That is a very good point. Thank you for pointing that out.</p>

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