Abstract
The functional life of paint in DoD is defined by the barrier properties and protective corrosion inhibiting capacity of the coating system. The time till corrosion initiation of an underlying substrate can thus be defined in general terms as 1) the time for an external environment to reach the coating/substrate interface through coating porosity, coating cracking, or mechanical damage and 2) inhibitor exhaustion/depletion. In other words, once a coating system has been breached, protection is afforded by the availability of inhibitors at the defect site. In this work, the parameters that influence inhibitor exhaustion will be examined. The onset of corrosion at a defect is a function of inhibitor release rate, the ratio of inhibitor to aggressive ions, and consumption of inhibitor in the vicinity of the defect. In this paper, the effect artificial inhibitor consumption on corrosion rate through the use of a flowing cell and a Multi-electrode Array probe will specifically be explored. The effect of flow rate on corrosion current will be shown for three different military primer systems. Steady state inhibitor concentrations at each flow rate will be used to explain the individual effects of flow and chromate content on corrosion current.
