Tannin Rust Converter TAC-30 (Over-Rust Coating, Phosphating)

Rust converters (tannin or phosphoric acid type) can chemically stabilize light surface rust (SSPC-SP2/SP3 grade) for direct overcoating. However, they cannot penetrate thick scale (>80 μm), laminar rust, or mill scale. For heavy rust, mechanical removal (blast cleaning to Sa 2.5 minimum) is still required before applying a high-performance coating system. Rust converters are best used as a supplementary treatment in maintenance repainting of structures where full blast cleaning is impractical—they buy time and improve adhesion but do not substitute for proper surface preparation in new construction or severe service.