Electrochemical Study Of The Corrosion Protection Of Stealthy Materials

To review the corrosion-resistance properties of low infrared emissivity coatings and predict their lifetime, electrochemical measurement techniques including polarization curves (Tafel) and electrochemical impedance spectroscopy (EIS) techniques were employed to investigate the electrochemical corrosion behavior of three different series of low infrared emissivity coatings in simulated sea water(3.5 wt.% NaCl aq. solution). The coating series concernd includes polyurethane-based and EP modified PU-based coatings in which were filled with Cu powder, Cu powder modified by silane coupling agent , and Cu powder modified by acrylic acid respectively. EPDM and EPDM-g-MAH-based coatings filled with Cu powder were also investigated in detail. The corrosion-resistance properties of coatings were evaluated and concluded by comparing Eocp, Rcoat , Ccoat ,icorr and fb , of the samples under same conditions.The results show that at the initial stage of immersion, both polyurethane-based coatings filed with modified Cu powder behave a better corrosion-resistance. The degeneration of protection of the coatings to the substrate, however, begins to accelerate with the immersion time going on. As a comparision, the coating filed with unmodified Cu powder shows a much better protection ability. With the immersion time going on, water permeats through the coatings and causes a possible failure of protection and the process may accelerate due to the presence of hydrophilic groups, such as -COOH and -OC₂H₅ .For the series of EP modified PU-based low infrared emissivity coatings, the coating filled with Cu powder show a better protection to the substrates at the initial stage of immersion. With the time of immersion going on, the rate of protection failure tend to accelerate. It exhibits the the worst for its protection ability. But the coatings filled with acrylic acid and silane coupling agent modified Cu powder exhibit a much better corrosion-resistance ability.Cu powder filling EPDM and EPDM-g-MAH-based coatings can not prevent the penetration of corrosive species through the coatings effectively and, as a result, coatings become failure in a short time and lead to a poor protection ability.