Kinkaku's Jinchūriki Forms

Despite not being a full jinchūriki, Kinkaku, like his brother Ginkaku, absorbed a massive amount of chakra from the Nine-Tailed Demon Fox while being trapped in its stomach. Thus, they can be considered "pseudo-jinchūriki" and have access to powers and abilities similar to that of Naruto Uzumaki.

Six-Tailed Form
While enraged, Kinkaku can access a massive amount of Nine-Tails' chakra, enough to form not only the cloak, but the "Version 2" that Killer Bee has in this form. He is presumably covered in the same mass of corrosive chakra. In comparison to Naruto's version, Kinkaku's six-tailed form lacks the Nine-Tails' skeleton that Naruto gains due to having the actual beast sealed within him.