Does anyone have any suggestions for me to improve my macro-etch test results?
I don't see much if any change from before and after I apply the acid.
Currently, after using a band saw to cut off 1" from each end, I have used the dyna file to polish the end before applying the muriatic acid. I dab some acid on a rag and wipe it on the piece, let it sit up to a couple of hours but it doesn't seem to do anything. I tried polishing the ends because when I didn't and etched it I didn't see a change then either. What can I be doing wrong?
Iv'e seen pictures of what's supposed to happen, how the weld and the base metal appear different shades from each other, but not mine.
I have noticed that when I use a nice new band saw blade, the edge I'm left with shows the fusion (or not) clearly, sometimes I wish I didn't have to etch it, but I do becuase it's called for.
Any thoughts are appreciated.
Thanks Chris
Take a small glass caserole dish and put about 1/8 inch of the acid in it. Place the weld face down in the acid bath for 5 minutes. Pull it out and rinse off with water. As soon as the water dries, spray a light layer of laquer over the weld to keep it from getting cloudy. My guess is that just putting it on a rag and wiping the surface is not getting enough acid on the part before it evaporates.
Beware of the fumes from the muratic acid, it burns the nose when you get a good wiff.
The test plates are either A572-50, or A36 steel.
I'll try letting it sit in a "bath" and see if that works. Thanks
Today, I tried it your way, by having the piece sit in a bath of acid, worked great, now it looks like was I was expecting it tol ook like. I suspected the guy who told me to do it the other way didn't know what he was going.
I went out today and purchased a container to be able to do this properly from now on, Thanks for all your help everyone. Chris
That's what this froum is for!!!
What I use is a small squeeze bottle with a dropper lid to apply the acid, I can control where the acid is applied. I let it sit and bubble and do it's thing, then gently use a light stream of water from a different squeeze bottle to neutralize and stop the etching. Like has already been mentioned...quickly spray on a coat of poly to seal out the air and your etching will remain for quite some time. Keep your head out of the fumes...they are quite irritating to the nose.
By Smokey71 
Date 02-03-2007 21:39
Edited 02-03-2007 21:42
3-m makes Roloc discs for sanding in a scotch brite type material, Brown for heavy, red for medium, blue for fine. Used in that order and then using a dropper to applie acid works best. i never touch the area after etching but rather rinse with tap water and blow dry with compressed air, then apply a thin coat of krylon clear coat. This really brings out the definition of the weld. we also have a poishing table but the Roloc discs are much much faster with equally good results! Hope this helped! P.S I quess i lied, i don't used a dropper really. It's a glass rod that has a small ball on the end. dip in acid and the ball holds the acid susspended til u touch the surface. then u can rub the area and move the acid around, appling more as needed.
I see you have a lot of help already. I find nitric works immediately without a bath on ferrous, just a swab (under a chem hood or proper ventilation with chem gloves and face shield) As long as the surface is polished smooth enough. If the piece is a little warm, works even better. I agree that sealing with laquer is a great technique. A quick reference for etches is QW-470 Etchants in ASME Section 1X, there it will tell you 1 part acid to 3 parts water for the Nitic etch(always add acid to water of course) Lepito's etch works really well too, but usually listed for nickel base materials and more tedious to make up.
What material are you etching, this information would facilitate more responses. Check out this past topic it might be helpfull
