A well fracturing component has a steel body with at least one passage and a connector for connecting the body to a source of pressurized frac fluid containing particulates for injecting into a well. An epoxy-based primer layer bonds to a side wall of the passage. A siloxane topcoat layer bonds to the primer layer. The topcoat layer has a greater thickness than the primer layer. The topcoat layer has less hardness than the primer layer and loss hardness than the body.