I heard the expression in a YouTube video, spoken by a French native (a teacher) to describe the state of his English. I understand the meaning to be "it's a bit rusty". I had never seen the expression before, so I searched around the Internet and found a comment saying it would not normally be used, even in informal French.
I have 2 questions:
- Is this really an expression that is used in colloquial French?
- Why is "rouillé" (rusty) not used rather than "oxidised"?
I look forward to your comments.