A novel, one-step, low-VOC, primer for the corrosion protection of aerospace alloys and metals.

摘要

Chromate-based technology used currently in the aerospace industry provides excellent corrosion protection for the aerospace metals and alloys such as AA 2024-T3. However, chromates are toxic and carcinogenic and the Environmental Protection Agency of the United States has identified chromates for replacement. This has resulted in a global research effort to find an effective alternative.; In this dissertation the above problem has been addressed through the development of a novel primer system consisting of silanes and resins (called Superprimer from hereon), which obviates the need for any pretreatment and offers a low-VOC, water-based polymeric coating which can be loaded to high levels for the corrosion protection of the substrate and result in a chromate-equivalent performance.; The initial results of various systems tested are reported. The silanes used for formulation of these preliminary formulations were bis-[triethoxysilylpropyl] tetrasuflide and bis-[triethoxysilylpropyl] ethane, used individually and in combinations of with various ratios. The resins used were an acrylate copolymer and a bis-phenol A-type epoxy. The results of various performance evaluation tests are reported in this chapter.; As a second part of this research, efforts were carried out to optimize the five systems discussed in Chapter 3. A Taguchi method approach was used for this and L9 orthogonal arrays were used to determine the ideal formulation for each of the five systems that were to be optimized. The results of this optimization study are reported in Chapter 4. It was found that all the 5 optimized systems gave improved performance and the bis-[triethoxysilylpropyl] tetrasulfide-based Superprimer performed the best.; The characterization of the bis-[triethoxysilylpropyl] tetrasulfide-based Superprimer coatings for development of models to explain the corrosion protection mechanism, cure chemistry and interfacial adhesion forms the third part of this dissertation. This has been discussed in Chapters 5, 6, 7 and 8. The characterization was conducted using SEM/EDX, FTIR-ATR, NMR and TOFSIMS to understand the structure, cure and solution chemistry and metal-primer interface of the coating system. Chapter 9 discusses the general conclusions, a summary of the proposed model for the mechanism of corrosion protection and the current status of research.