Hexavalent chromates have long been recognized as the "gold standard" in corrosion protection.  However, increasingly stringent health and environmental regulations are restricting the use and disposal of the chromates.  The primary mechanism by which chromates arrest corrosion on aluminum alloys is through inhibition of the oxygen reduction reaction (ORR) at copper containing cathodic half-cells.  Other inorganic anions and inorganic cations are much less effective than chromates. Recent studies have shown that Ce³⁺ is 1000 times less effective than CrO₄^2- at inhibiting the ORR, whereas certain organic thiols (e.g. 2,5-dithiol-1,3,4-thiadiazole) are only 100 times less effective than chromates as inhibitors. TDA has used a rotating disc copper electrode and computational modeling to develop Quantitative Structure Activity Relationships for organic inhibitors of the ORR.  We will present the results of these studies and discuss the relationships between the organic structures and inhibition of the ORR for developing improved organic corrosion inhibitors for aerospace aluminum alloys.