From these findings a model of different corrosion pathways was derived, which suggests that the anodic part reaction quickly propagates forward along the grain boundaries and is escorted by the local cathode. It can be said that on the delaminated substrate surface the main corrosion front can spread out more easily. Based on this model the corrosion propagation would decelerate by inhibiting the grain boundary activity. The second part of this study focused on the design of polymeric material and its selective application to grain boundaries. The anodic dissolution ability of grain boundaries and the preferred release of aluminum cations were thus used for the selective application of corrosion inhibiting materials on these active sites. An initial applicability screening of materials towards grain boundaries showed promising results with autophoresis of water-borne dispersions; among phosphating and surface spontaneous polymerization. Based on these results water-borne block-co-polymer dispersions were synthesized containing adhesion promoting groups such as carboxylic acid, phosphonic acid and triethoxysilane. Application of these polymers exclusively on grain boundaries could be realized with a controlled release of aluminum cations from these weak spots. It was shown that in the pH region of 2.5 to 4.0 grain boundaries start to dissolve and that coagulation of dispersed polymer particles is susceptible towards triple charged aluminum cations. This combination led to selective deposition of polymer particles on grain boundaries. The final proof of concept was provided by a comparison of nongrain boundary treated versus grain boundary treated HDG substrates in a salt spray test.