Crystallographic texture of light tinplate coatings made in various electrolytes

Two electrolytic tinplating processes are currently used in Europe: PSA (based on phenolsulfonic acid) and MSA (based on methanesulfonic acid). The Halogen Process is used in other parts of the world. The electrolyte composition and process parameters affect the electrodeposit and ultimately the tinplate appearance and performance. In order to better understand the impact of electrolyte composition on the crystallographic texture of tin coating tinplate, light tin coatings on single reduced, continuously annealed (CA) tinplate produced in three electrolytes: Halogen, PSA and MSA were analyzed. The crystallographic texture of thin tin coating (<2.8gm-2) was analyzed by X-ray Diffraction and Electron Backscatter Diffraction. The effect of reflow (melting of the tin followed by rapid solidification) and ironing during drawn and wall ironed (DWI) can forming on the tin crystallography were evaluated. Both texture analysis by XRD and EBSD confirmed that all un-melted tin coatings, made in three different electrolytes, contain texture fibers. The effect of steel sheet crystallographic texture was investigated by comparing the tin crystallographic orientation on continuously annealed steel substrate (with α and γ fiber texture) versus batch annealed (BA) steel with a strong γ fiber texture. The main electrolytic parameters, current density and line speed, did not affect the texture formation of tin coating produced in MSA-based electrolyte within the commercial ranges. Un-melted tin coatings produced in the MSA-based electrolyte showed sharper texture than those produced in PSA and Halogen electrolytes. The FeSn2 alloy structure was not observed in un-melted tin coatings; however, it was detected after ironing in the DWI process.