How to remove the boundary between different types of mesh

Hello there,

I’m currently using paraview to post-processing my data from Fluent. I exported the data in CGNS format. I use a combination of structured and unstructured mesh which are connected by an interface. When I do the post-processing, the interface becomes a surface, also when I draw the iso-surface, there is a black boundary line between the unstructured and structured region. It really looks ugly. So I am wondering if anyone knows how to remove this black line and kindly help me. Thank you very much.