SK-5 flaking and breaking off while sharpening?

[DMG]

There is plenty of acids that would do absolutely nothing to rubber and coating, while completely dissolving the steel.
Even stainless steel will disappear in Nitric acid as it attacks both, Iron and Chromium and both of these salts are soluble in water.
Now, nitric acid is very good at attacking metals, and would be my first choice to dissolve metal as it's also an oxidant.
Lotd of metal oxides are made by dissolving metals in nitric acid and then heating the salts until they decompose to metal oxide and gasses.
Now, I doubt he exposed the knife to such chemicals, but you never know.
Nothing is indestructible, and as plain carbon steel is almost pure Iron - it's fairly reactive, and we all know corrosion is one of weak sides of plain carbon steels.

Which of those processes would allow the knife to remain shaped like a knife and only appear damaged when someone attempts to sharpen it?