This application relates to an enclosure for a portable electronic device. The enclosure includes a metal substrate and a dehydrated anodized layer overlaying the metal substrate. The dehydrated anodized layer includes pores having openings that extend from an external surface of the dehydrated anodized layer and towards the metal substrate, and a metal oxide material that plugs the openings of the pores, where a concentration of the metal oxide material is between about 3 wt % to about 10 wt %.