AbstractNew concept of remountable first wall using liquid flow has been proposed as a different approach of liquid wall concepts like APEX (Abdou, the APEX team, Fusion Eng. Des. 54 (2001) 181). In this study, the numerical analysis of MHD flow has been carried out to evaluate effect of coating on the MHD pressure drop. In the proposed concept the liquid layer is sandwiched by two metal plates with two side ribs to compose the flow channel. The numerical results indicate that coating the whole rib surface has good performance as three surface coating to reduce the MHD pressure drop. In both cases of flibe and lithium coolants, the solid metal (HT-9) wall can be used by coating with the insulator whose electric conductivity ratio (σcoating/σHT-9) is less than 10−6 under 6 T.