This etched specimen is a 226g Gibeon, the only slice I've kept from the first Gibeon I cut, more than twenty years ago. Gibeons are known to be exceptionally stable, rarely needing special attention. Aside from an initial application of G-96 right after it was etched, the piece remained on the display shelf for many years in completely pristine condition. Several years ago I decided to bring it along to a number of outreach sessions. Expecting it to be handled quite a bit, I gave it several coats of lacquer to ward off fingerprints that could potentially leave marks on the etch. The lacquer also seems to improve the contrast of the etch. Over time though (years), a couple of corrosion streaks appeared.
Whether there was trapped moisture present in the plate boundaries, or the lacquer penetrated and somehow reacted there, I'm uncertain. The rust spots are stable, no changes have occurred since they first appeared. They are an annoyance though, on an otherwise perfect specimen. Similar pieces have only been given the G-96 treatment and they remain rust free. Recommendation; avoid sealants that can cause issues that are so readily avoided.
Lee