4,4,4-Trifluorobutanoic acid-d4 is the labeled compound of CAS# [406-93-9] and is used in electrochemical studies as a corrosion inhibitor for iron in mineral acids. It is also a hydrophobing compound which forms a fluorocarbon-like surface without sacrificing adsorbability in order to determine corrosion rates of Fe in 3N HCl with and without 4,4,4-Trifluorobutanoic acid-d4 by using potentiostatic polarization.