Self-limiting film formation mechanism of zirconium based conversion coating on mild steel

Purpose - The purpose of this paper is to investigate the film formation mechanism of zirconium-based conversion layer on mild steel. In this way, different approaches were used to show the self-limiting film formation mechanism. Design/methodology/approach - To determine this mechanism, film formation was detected using DC polarization, spectrophotometric technique and surface analysis techniques, including field emission scanning electron microscope (FE-SEM) and atomic force microscopy (AFM). Findings - DC polarization resistance of surface increased with increasing of mild steel immersion time in the conversion coating bath, reaching to a plateau region. On the other hand, zirconium ion concentration decreased during the beginning of the film formation process and continued with a constant concentration, showing the expiry of the process after some minutes. Originality/value - This paper deals with the film formation mechanism of the zirconium-based conversion layer that includes valuable findings to monitor the process.