An apparatus may include: a body defining a flow path; an inlet to the flow path; an outlet to the flow path; a test coupon at least partially disposed within the flow path; a sealing element disposed between the test coupon and the body; and a current source electrically coupled to the test coupon, wherein the inlet and the outlet are in fluid communication through the flow path, and wherein the sealing element electrically insulates the body and the test coupon.