Hi, Ron. You're right to be surprised, I would be too.
The EDS and SEM are relatively new and are calibrated regularly. It is also used reliably every day for failure analysis. I have not seen a reason yet to doubt the EDS detector/analyzer. There may be sulfur present, but in trace...
We put a sample in our SEM and ran EDS. Main elements present: aluminum (obviously), but also silicon, oxygen, and some magnesium, but no sulfur. The amount of silicon present on the surface is far beyond the 10wt% in the alloy. We thought that maybe our P2 etch bath had contaminants which...
P2 etch (ferrous sulfate, sulfuric acid, DI water, 160F, 25 minutes) is needed on aluminum at my facility prior to application of a structural primer paint on the aluminum. This is fine on wrought aerospace alloys like 2024, 6061, 7075. Today we tried an alloy similar to an A356 aluminum...
