In general oilfields have less gas pressure as they mature. As a result ingress of oxygen into well annuli into the vapor space in tanks and through pump packing becomes more commonplace. Consequently it is possible for severe localized corrosion (> 12 mm/y) to occur. Unfortunately there are very few options to control very high corrosion rates arise due to oxygen ingress. This is because common corrosion inhibitors generally fail to protect carbon steel when oxygen is present. In this paper we report an improved performance of a second generation of novel phosphate ester based inhibitors. These inhibitors showed superior performance in comparison with previously reported products effective for oxygen corrosion. They are capable of protecting carbon steel from carbonic acid corrosion and from the combination of carbonic acid in the presence of high oxygen levels. They mitigated oxygen induced corrosion by creating a chemisorbed film on oxidized metal surface. The electrochemical reaction mechanisms involved in this process is described.