As much as I love Engineer Guy videos, I am especially partial to Series #4, because it is themed around the chemical elements—each installment features a different element and a remarkable bit of engineering based upon it. And this week my two personal favorite elements are in the spotlight. Though it is utterly common, today, metallic aluminum was once among the most precious metals in existence. Books can and have been written about aluminum’s wonderful history and properties, and as for titanium…well, who doesn’t love titanium?

Here, then, is the third installment of Engineer Guy Series #4, in which Bill Hammack (and his behind-the-scenes teammates Patrick Ryan and Nick Ziech) take us through the constructive use of corrosion to create durable, colorful surface finishes on, for example, Apple’s laptops and iPods. Great, as always. [Thanks, Bill!]