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Up Topic American Welding Society Services / Certifications / Acid Etch questions
- - By PFI (**) Date 07-17-2012 20:10
we test our weld processes Internally and require acid etching for most of our acceptance criteria, we have a variety of recipes (for lack of a better word) for the etching of stainless, We are currently are using what seems to be the best recipe we have and it's effectiveness seems to be lacking, It could be because some of the chemicals are outdated, but before we purchase all new chemicals i want to see if anyone has had good luck with a particular mix, what is the best recipe for etching stainless (weld profile) 304 and 316 mostly?

Thanks for any replies
Parent - - By TimGary (****) Date 07-18-2012 10:32
AWS B2.1 : 2009 recommends the following for Stainless:

Ferric Chloride (FeCl3)   200g
Nitric Acid (HNO3)        300ml
Water (H2O)               100ml

This solution should be used at room temp and applied by swabbing.
Remember when mixing acidic solutions, always add acid to water.
Never add water to acid.

Tim
Parent - By 99205 (***) Date 07-18-2012 17:12
A face shield, goggles and rubber gloves would be a good idea too.
Parent - - By PFI (**) Date 07-18-2012 19:20
Tim;

I will have to try that one, didn't know about adding the acid to the water and not vice versa, is that for safety reasons? or effect?

I had a reply from a local testing facility and here is what they recommended ....

                       4 grams CuSO4

                        20 ml HCl

                        20 ml water

have you heard of this one?
Parent - - By welderbrent (*****) Date 07-19-2012 04:20
In Jr High and High School Science classes we were always taught 'Always Add Acid' (triple 'A').  Easy to remember.  It just flows.

It is for safety.  If you view a splash effect in slow motion the water will be your splash agent when adding the acid.  Thus, you don't want acid to be what is splashing by adding water.  You will also have a small amount of acid to deal with in the solution as you begin, versus a large amount of acid if adding water and something went wrong.

Have a Great Day,  Brent
Parent - By PFI (**) Date 07-19-2012 10:02
ahh gotcha, Thanks for the info!
Parent - By TimGary (****) Date 07-19-2012 11:21
Nope, Haven't heard of that one.

The safety note is to reduce the chance of splashing acid on yourself, as Welderbrent said.
Even though, the mixing and use of these potent acids is hazardous.
Proper PPE is a must.

Tim
Up Topic American Welding Society Services / Certifications / Acid Etch questions

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