Problem etching CPM 3V

John Barker

John Barker

SUPERModerator & KNIFE MAKER
I usually etch my CPM 3V in a 50/50 mixture of Ferric Chloride and distilled water. I've etched several blades with my current solution which is about 3-4 months old. In fact I etched a blade 2 weeks ago and it came out fine. Last night I etched two CPM 3V blades and they had this pattern on the blades that looked like a splash kind of pattern. The pattern was rather fine and scattered. Before etching the blades I cleaned the with acetone, then washed them with dish soap to remove any oil. Let them sit overnight and then cleaned them again with denatured alcohol before etching them. They sat in the solution for 5 minutes. These two blades are from two different peices of 3V. One is 1/8" thick and the other is 5/32" thick. Any ideas. I don't think these are carbides. The blades had a 400 grit hand satin finished before the etch. I was was able to sand the pattern out, and tried it again for seven minutes with the same outcome. I was thinking about trying vinegar.
-John
 
Is your FeCl contaminated possibly? I know that sometimes I'll get stuff floating on the top of the solution that will stick to the blade as it goes into the tank. Try soaking up any gunk from the top of the tank with a paper towel. Also, when you put the blade in, dunk it in and out a few times to break the surface tension of anything that might be floating on the top.

-d
 
John , I would try some hot/ warm lemon juice , sounds like a defect in steel ? or maybe the etch is too strong ?? interested in what happens . I was going to buy some 3 V ? . Bubba
 
Deker,
I keep it enclosed in a plastic container and I don't see anything floating in it. I guess I could strain it to be sure.

Bubba,
I don't think it's the steel, because they came out of 2 different batches and the one I etched 2 weeks ago from the same 5/32" stock came out fine.

-John
 
Seems like your steel is clean and you used two different bars, so it almost has to be the etchant.

Mix a fresh batch of etchant and try again. Just because a solution looks clear to the naked eye, doesn't mean it's pure and has the same properties it did a week or two ago. There are all sorts of factors that can mess with any chemical, including temp, humidity, contaminants, exposure to oxygen... etc.
 
CPM3v is often etched in this manner to "passivize" the surface. This helps with corrosion resistance. Kinda/sorta like bluing a gun but not exactly.
 
Ernie,
It doesn't work on stainless.
Could tiny bubbles on the surface of the blade do this?
-John
 
can you get a picture of it?
use that crazy thing you look into peoples eyeballs with..that should get a nice close up..
 
I already sanded off by hand. It's sitting in vinegar right now... I may try it on another blade later tonight. I don't have time for this right now. Blade is next week!
-John
 
I made up a new solution of Ferric Chloride and distilled water, but it is very weak. Like 10 parts water to 1 part ferric chloride and kept the knife moving in the solution for about three minutes. Worked great. I really think I had bubble on the blade. Thanks for all the input guys.
-John
 
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