Corrosion Science and Technology

The Corrosion Science Society of Korea (한국부식방식학회)
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Characterizing the ac-dc-ac Degradation of Aircraft and Vehicle Organic Coatings using Embedded Electrodes

  • Bierwagen, Gordon P. (Department of Coatings and Polymeric Materials, North Dakota State University) ;
  • Allahar, Kerry N. (Department of Coatings and Polymeric Materials, North Dakota State University) ;
  • Su, Quan (Department of Coatings and Polymeric Materials, North Dakota State University) ;
  • Victoria, Johnston-Gelling (Department of Coatings and Polymeric Materials, North Dakota State University)
  • Published : 2007.10.31
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Abstract

Embedded sensors were used as an in-situcorrosion-sensing device for aircraft and vehicular structures protected by organic coatings. Results are presented changes associated with a standard Airforce aircraft coating and a standard Army vehicle coating were monitored by embedded sensors. These coatings consisted of a polyurethane topcoat and an epoxy primer, however are formulated to provide different characteristics. The ac-dc-ac testing method was used to accelerate the degradation of these coatings while being immersed in a NaCl medium. Electrochemical impedance spectroscopy and electrochemical noise measurement experiments were used to monitor the induced changes. A comparison of the results between coatings subjected to the ac-dc-ac exposure and coatings subjected to only constant immersion in the NaCl medium is presented. The results were used to demonstrate the effectiveness of the ac-dc-ac method at accelerating the degradation of an organic coating without observably changing the normal mechanism of degradation. The data highlights the different features of the coating systems and tracks them while the coating is being degraded. The aircraft coating was characterized by a high-resistant topcoat that can mask corrosion/primer degradation at the primer/substrate interface whereas the vehicle coating was characterized by a low-resistant topcoat with an effective corrosion inhibiting primer. Details of the ac-dc-ac degradation were evaluated by using an equivalent circuit to help interpret the electrochemical impedance data.

Keywords

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