madhatta,

While Al-6XN has excellent pitting resistance, it is possible to produce this condition.  Are you using one of the methods outlined in ASTM G 48?  Elevated temperature is required even when using ferric chloride.  Use the following link for more information:

http://www.alleghenyludlum.com/ludlum/pages/products/xq/asp/P.40/qx/product.html#

Click on Technical Data Bluesheet

Will crevice corrosion do, or do you need pitting?
There are some ways to cheat and get failures, but I suppose that you want clean corrosion.
I'll give you info tomorrow, I am traveling.

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.
http://www.trent-tube.com/contact/Tech_Assist.cfm

Maybe a use for Green Death solution ('Severe Simulated Scrubber Solution' in the AL-6XN tech sheet);  see thread330-141116

Include welded test coupons.

Tell us something about your project.  The accelerated corrosion test should be relevant to the intended environment.

Just found this link, and thought it might be useful:

http://www.corrosionlab.com/papers/astmg48/problems-in-utilizing-astm-g-48.htm

"Tell us something about your project. The accelerated corrosion test should be relevant to the intended environment."

Sorry- I should have included some background. The AL6X in question is in a heat exchanger in a marine environment. They are having pitting problems- they feel it is a result of 'bio-fouling' ???
They have a surface conditioner they want to try and use, but first we have to do some mock-ups in the lab environment. Before we can do any testing on the efficiency of the surface conditioner, we have to get the AL6X to pit. Therein lies our difficulty.
Thanks for the information.
My coworkers are especially interested and impressed with the 'Green Death Solution' !!

Are your tubes AL-6X or AL-6XN?
If they are 6X, were they annealed after welding?

1. Your pitting is due to fouling.  Trust me on this.

2. If you are trying to simulate pitting by bio-fouling you should look at using 2% NaCl + KMnO.
You can pit samples at the boiling point.
Then clean them and treat them.
Try to pit again to see if it helped.

Face reality.  Bio-control and clean tubes is all that will help you.  Surface treatments may help for a short while, but it is a waste.
If the tubes are 6X they have been on service 25 years, what more do you want when you miss operate the unit?

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.
http://www.trent-tube.com/contact/Tech_Assist.cfm