A36 Plate Scale Removal

3 hours in the pickling bath - already seeing a good amount of bits sitting on the bottom of the drum and a good amount of bubbles forming on the surface. I plan on letting this go for 24+ hours then neutralizing in an alkaline bath (baking soda and distilled water) before lightly coating with oil to prevent any surface rusting as I continue on with the fabrication. I still plan to fly cut / surface the plate on both sides before locating and drilling/boring the many holes. This plate is destined to be my first tooling/fixture.

Since I am waiting for the carbide tooling to arrive for the surface operation I am in no rush.
 
Iceman said:
It's pickling in diluted vinegar - it's probably 6 cups of vinegar and 5 gallons of water. Tastes slightly acidic so hopefully it's enough to do the job.
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Dilute vinegar will probably not do it for you or if it does, it will take a very long time. You might try electrolysis. It works to remove rust and should work on the scale. I tried a piece of hot rolled mild steel. About 40 sq. in. and 10 amps of current. After about ten minutes, there was a noticeable decrease in the scale.
 
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I have played around with that method in the past with somewhat good results. I figured I would start with this. I actually have had my best results with an alkaline solution as the electrolysis medium for removing rust and electroplating.

And yes, I am the man with the "golden" monkey wrench.

-IM
 
So if I am unhappy with the pickling experiment I will use the neutralizing bath as an electrolysis medium and go that route next.
 
Iceman said:
3 hours in the pickling bath - already seeing a good amount of bits sitting on the bottom of the drum and a good amount of bubbles forming on the surface. I plan on letting this go for 24+ hours then neutralizing in an alkaline bath (baking soda and distilled water) before lightly coating with oil to prevent any surface rusting as I continue on with the fabrication. I still plan to fly cut / surface the plate on both sides before locating and drilling/boring the many holes. This plate is destined to be my first tooling/fixture.

Since I am waiting for the carbide tooling to arrive for the surface operation I am in no rush.
Click to expand...
You can speed it up a bit by brushing the crud off the surface of the part. It's going to be slow with vinegar, though.
 
image.jpeg Well wasn't seeing much activity in the acid pool - gave it a rinse in the part washer and built it a cozy alkaline bath with sodium carbonate.

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Before (but after pickling - which I do believe actually softened the surface material - easier to scratch with file)

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Careful application of some DC power-

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After and hour - just a light metal brushing:
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I dare say it is working.

I don't know why 2/3's of my pictures decide to orient themselves 90* anti-clockwise post-upload.

-IM
 
Its about 1-1/2 cup sodium carbonate (washing soda) to roughly 4-5 gallons of water. I can say, having used baking soda (sodium bicarbonate), that the washing soda appears more effective as an electrolysis medium. Just a note for those thinking about attempting this. The Rigol power supply is massively overkill in complexity and limited in its current output (it is designed more for electronics work than this). But with its complexity also comes excessive build quality and a continuous duty cycle. No worries about overheating, it is barely breaking a sweat.
 
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