The Transformers S02 E45 Cosmic Rust

"More than Meets the Eye!"

Megatron causes his fellow Decepticons to be infected with the deadly Cosmic Rust. Perceptor is captured to find a cure and he does, learning that element X will do the job. The Decepticons are cured, but then they use Perceptor to spread the Cosmic Rust to the Autobots and element X is in short supply.