How to check weld penetration. Acids,Bluing,Rusting, What works? My research revealed

[I_Love_Plasma]

For a long time I have been wanting to check my weld penetration like Jody does from "Weldingtipsandtricks.com" "down and dirty tips and tricks" by cutting the weld perpendicularly to the length. So I laid a pretty uniform bead of E7018 on uncleaned A-36 steel. I cut it cross wise with our plasma cutter. Then ground it back about an eighth of an inch or so to grind away from anything the plasma may have fused during the cut. then I smoothed out the angle grinder marks with a flat wheel 80grit. I knew that etching was done with acid. So I decided to try vinegar, it bubbled a little but the steel and the weld didn't change colors. So I carefully dipped a few drips of sulfuric acid from an automotive battery, it bubbled pretty fast, still no color changes. Okay I need a stronger acid! Gingerly I dripped about a cc of Hydrochloric Acid concentrate on the weld surface, it bubbled violently, yet no color changes took place. By now I was wondering how industry did etching so I Googled "How to etch mild steel" and I found out that industry uses nitric-acid. I don't have nitric-acid! I do have some glycerin around somewhere though , for those who know what I'm talking about Nitric-acid is wildly expensive and even worse is the hazmat fee that UPS charges. So I got to thinking about how a member here on the forum removed rust from his old wood jointer by using electrolysis. I knew in electrolysis the positive attracts oxygen molecules and the negative attracts hydrogen molecules. Hydrogen is not corrosive, oxygen is, ha ha watch out! So I reground my weld cross cut, sanded it with a flat wheel from 80 grit to old 220 grit. Then I used some mag wheel pumice polish on it until I could see myself in the reflection. Now I took the piece and placed it in a strong solution of drain cleaner (100% pure sodium lye, potassium lye works just as well). And made the welded piece positive with our 12amp 12VDC battery charger on the "manual charge" setting. I placed the weld surface into the electrolyte about a sixteenth of an inch, and a piece of 316L Stainless Steel on the other side as my negative electrode. This method works great!

Here are some pictures of the cross cut weld after about 30 minutes of electrolysis.
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The cost is basically free, especially compared to about $50-100 dollars for a tiny bottle of nitric-acid.

USE EXTREME CAUTION WHEN ELECTROLYSIS IS OCCURRING! HYDROGEN AND OXYGEN GASES CAN BUILD UP CAUSING A POTENTIALLY FATAL EXPLOSION IF THE GASES ARE IGNITED! IT TAKES A 14 NANO JOULE SPARK TO SET OFF HYDROXYL GAS (MUCH LESS THAN A LIGHTER, OR A BRUSHED MOTOR PRODUCES)! BE SAFE!

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