Porcelain? It’s used on bathroom fixtures, often times as a top coating, or enamel.
20180522/https://en.wikipedia.org/wiki/Porcelain
20180522/https://en.wikipedia.org/wiki/Industrial_porcelain_enamel
20180522/https://en.wikipedia.org/wiki/Vitreous_enamel
Interesting. Glass-enameled steel can be used for “graffiti-proof” public infrastructure.