'Rust' in the Bible

Therefore thus says the Lord Yahweh: "Woe [to] the city of bloodguilt! A pot that [has] its rust in it; {its rust did not go out from it}. Bring it out {piece by piece}; {one is as good as another}.

And {make it stand} empty upon its burning coals so that it may become hot, and its copper may become molten and be melted in the midst of it, [so that] its uncleanness and its rust be consumed.

[Through] effort she has caused weariness; {its thick rust} went not [out of] it. Its rust! Into [the] fire [with] its rust!