*Article* **Microstructure and Corrosion Behavior of Iron Based Biocomposites Prepared by Laser Additive Manufacturing**

**Yan Zhou <sup>1</sup> , Lifeng Xu <sup>1</sup> , Youwen Yang 2,\* , Jingwen Wang <sup>1</sup> , Dongsheng Wang 1,\* and Lida Shen <sup>3</sup>**


**Abstract:** Iron (Fe) has attracted great attention as bone repair material owing to its favorable biocompatibility and mechanical properties. However, it degrades too slowly since the corrosion product layer prohibits the contact between the Fe matrix and body fluid. In this work, zinc sulfide (ZnS) was introduced into Fe bone implant manufactured using laser additive manufacturing technique. The incorporated ZnS underwent a disproportionation reaction and formed S-containing species, which was able to change the film properties including the semiconductivity, doping concentration, and film dissolution. As a result, it promoted the collapse of the passive film and accelerated the degradation rate of Fe matrix. Immersion tests proved that the Fe matrix experienced severe pitting corrosion with heavy corrosion product. Besides, the in vitro cell testing showed that Fe/ZnS possessed acceptable cell viabilities. This work indicated that Fe/ZnS biocomposite acted as a promising candidate for bone repair material.

**Keywords:** iron bone implant; zinc sulfide; degradation properties; passivation film; laser powder bed fusion
