Fundamental study of corrosion preventive compounds: Part I—Formulation and characterization

Hard film corrosion preventive compounds (CPCs) were formulated based on the general composition of a commercial CPC. The homemade CPC was composed of a combination of resins, organic solvents, and corrosion inhibitor. The corrosion protection provided by the commercial CPC and homemade CPCs applied to Al alloys and 1018 carbon steel was assessed using the ASTM B117 salt spray test. The CPC containing Mg sulfonate inhibitor and the commercial CPC performed the best, and the CPCs without corrosion inhibitor or with Na sulfonate inhibitor performed the worst. No or slight corrosion was visible on Al alloys coated with the commercial CPC and the best homemade CPCs after 500 h of salt spray exposure. Electrochemical impedance spectroscopy (EIS) testing was used to assess the degradation of CPCs on AA2024-T3 samples immersed in NaCl solution. CPCs showed better performance during immersion than in the salt spray environment. EIS testing was also used to show that homemade CPCs can displace water from a water-saturated primer. The compositional profiles of CPCs both before and after salt spray exposure were determined using glow discharge optical emission spectroscopy. There were only small changes in the thickness of the commercial CPC and the homemade CPC containing Mg sulfonate inhibitor after salt spray exposure, while the thickness of the homemade CPC containing Ba sulfonate inhibitor was largely reduced after exposure.