From Teletraan I: The Transformers Wiki

Scraplets are a disease found in the Generation 1 continuity family.

Scraplets is alleged to be the deadliest disease known to mechanical lifeforms in the entire galaxy. A single scraplet resembles a tiny robot that can transform itself into something that appears to be a harmless nut or bolt, but they can self-replicate with incredible speed and embed themselves en masse into the skin of a mechanical organism, and over time, digest the victim nat by nat.

There is no known cure for scraplets other than a legend that claims a "rare chemical" was once discovered (and subsequently forgotten) that could kill the scraplets.

Spoiler warning: Plot and/or ending details follow.

This "rare chemical" was water.