Plasma cutting leaves a small slag edge on the bottom and sometimes on the top called dross. This can usually be removed easily with a file or grinder. We will remove most of the heavy dross and the parts will be suitable in most cases to use as is. If you are going to use the parts in a welding application then you probably have the tools needed to clean the part further if needed and as you see fit. Edges of the cut parts can sometimes be sharp. Be carefully when handling.  If you buy a completed or painted part, you do not have to worry about this.