Alrighty.  So I do some informational PT in my small shop, and I would like to be able to etch the surface, .0004"-.0007" or so just to remove any smearing.  This will be exclusively for aluminum.  Does anyone know of a method of performing a localized etch, i.e. just the weld and HAZ?  I tried searching a bit, but no dice in the forum here.  Thanks in advance.