Transformers Generation 1 - Season 2, Episode 27 - The Golden Lagoon

Fierce action leads both Beachcomber and Thrust to stumble upon electrum, a liquid key to invincibility. There is a forest lagoon's worth of the stuff, but only the Decepticons succeed in making a claim. The results, of course, render the Autobots' weapons essentially useless. The only hope that the Autobots have is to try to fight fire with fire, but Megatron isn't about to give them the chance. What price must be paid for victory?