Note the verb pattern: rust 'grows on' or 'forms on' something — 生铁锈 / 长铁锈 (lit. 'grow rust'). The English 'iron has rusted' is most naturally 铁生锈了 (tiě shēng xiù le).
culture
By extension, 铁锈带 (tiěxiù dài) is the Chinese term for the American 'Rust Belt' — the deindustrialized Midwest. It surfaces often in news commentary on US politics.
