Tin Free Steel Sheet Fabrication Flow
Tin Free Steel (TFS), also named chrome-coated steel sheet, is a core packaging material widely used for food cans and metal containers, whose standardized fabrication follows continuous streamlined procedures from raw steel coil to finished chrome-plated sheet products. The whole production route is divided into base material preparation, pre-plating surface treatment, dual-layer chrome electroplating, post-plating finishing and final quality inspection.
The fabrication starts with uncoiling of cold-rolled low-carbon steel coils, the fundamental substrate of TFS. Consecutive steel coils are welded to realize uninterrupted line operation, then strip steel enters tension straightening equipment to eliminate surface camber and internal stress for uniform flatness. Next comes multi-stage cleaning: alkaline electrolytic degreasing removes rolling oil and surface organic contaminants, followed by dilute acid pickling to clear iron oxide and rust film; repeated deionized water rinsing after each cleaning avoids residual chemical liquid damaging subsequent plating adhesion.
Core chrome plating adopts mature two-step electrolytic deposition technology. In the first plating tank, pure metallic chromium is electrodeposited onto cleaned steel surface under stabilized current density to form dense anticorrosive base coating. Then the strip moves into the second bath for chromium oxide film formation, which boosts paint adhesion and surface abrasion resistance, the dual composite coating is the key feature distinguishing TFS from tinplate. Strict temperature and electrolyte concentration monitoring runs throughout plating to prevent uneven coating thickness or coating peeling.
After plating, surplus chromate solution is fully washed off via cascade rinsing. Anti-rust oil is uniformly coated on sheet surface for short-term storage protection, then edge trimming cuts strip into customer-specified width and removes irregular side scraps for recycling.
The final procedure is comprehensive quality control. Inspectors test coating thickness, surface gloss and flatness with precision instruments; defective sheets with pinholes or coating defects are sorted out. Qualified TFS sheets are recoiled into finished coils for subsequent slitting and blanking fabrication according to downstream processing demands. Controlled process parameters guarantee stable corrosion resistance and printing performance of finished chrome-free steel sheets.
