| dc.description.abstract | The deterioration of metallic components in caustic environments is a problem that has safety and monetary repercussions. The effects of corrosion and thermal degradation on steel are issues that have plagued manufacturers and industrial end users alike, resulting in the need for excessive engineering, monitoring and repair. Even with these drawbacks, the natural abundance and high strength of steel keeps it widely used. Barrier coatings exist to protect the vulnerable metal, acting as insulation between the corrosive agents and high temperatures to ensure the preservation of the desirable mechanical properties. Unfortunately, the best commercially available barrier coatings are either hazardous to the environment, as is the case for corrosion protection, or expensive, such as the ceramic thermal barrier coatings. Layer-by-layer assembly has been extensively used in the creation of polymer nanocomposites thin films for a number of barrier applications. This dissertation describes methods to functionalize polymer-clay thin films to improve their barrier properties for corrosion and thermal protection.
Nanobrick wall coatings have demonstrated high gas barrier properties but do not hold up to corrosive agents. Crosslinking of the polymer matrix and silanization of the substrate prior to deposition improves the corrosion barrier. Crosslinking leads to the reduction of water uptake in the polymer and silanization improves the adhesion at the interface between the substrate and thin film. The combined functionalization creates a successful primer layer when tested in a multilayer insulating coating, which remains effective for at least five days.
Similar nanobrick wall coatings have been used as flame retardant barrier coatings. The addition of an amine salt buffer in the deposition process, and a higher concentration of polymer, generates a thick microscale coating that acts as a heat shield when applied to steel. In this dissertation, a 14-bilayer film is shown to thermally protect steel, through the creation of a macroscale insulating bubble. The performance is comparable to commercially available ceramic thermal barrier coatings but is more cost effective and has a simple deposition process.
Char promoting additives are utilized to improve the observed barrier property of these thick nanobrick wall films. These additives influence not only the char generated but also the architecture of the film during pyrolysis. The creation of a more complex structure with varying nano and microdomains, in addition to the macroscale bubble, hinders thermal diffusion and further improves the heat shielding property of these unique coatings. | |
