E-Thesis 74 views 62 downloads
Novel Galvanic Coatings for Airport Ground Support Equipment / DANIEL MURPHY
Swansea University Author: DANIEL MURPHY
DOI (Published version): 10.23889/SUThesis.69887
Abstract
The motivation for the work presented in this thesis is the need for a low-temperature solution for the corrosion protection of steel Ground Support Equipment and the repair of failed hot-dipped galvanised (HDG) components. With this development, it is hoped that lead time on projects and some overh...
| Published: |
Swansea University, Wales, UK
2025
|
|---|---|
| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | EngD |
| Supervisor: | Penney, D. J., and Sullivan, J. H. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa69887 |
| Abstract: |
The motivation for the work presented in this thesis is the need for a low-temperature solution for the corrosion protection of steel Ground Support Equipment and the repair of failed hot-dipped galvanised (HDG) components. With this development, it is hoped that lead time on projects and some overhead costs will be cut. This would be potentially possible as the need to outsource galvanising would be no longer necessary.Hot-dip galvanising can be an expensive process with the need to transport large products to dedicated galvanising baths making it logistically inefficient and costly.Another issue is the repair of galvanised products, often leading to the expulsion of toxic Zn fumes and leaving the repaired area unprotected against corrosive attack.Zinc-rich paints (ZRPs) are a commonly used coating in the repair of HDG. Several issues are reported with conventional zinc-rich paints and the need for a moredurable and protective solution for steel components is evident.To achieve this, a novel coating is developed using zinc-rich paints as a model, instead replacing the organic/inorganic binder with a metallic matrix. The inclusion of a metallic component with the zinc, seeks to overcome the adhesion and deterioration failures often found in ZRPs.Bismuth-tin (Bi-Sn) fusible alloy was chosen as the metallic matrix component for a new coating, owing to its well-known low-temperature properties that see it utilised across industry and society. To develop the coating, various Zn loadings in Bi-Sn were trialled and analysed via scanning electron microscopy of the resulting microstructure. Time and temperature of heat treatment were also analysed in the same way. It was found that a composition of 20 wt% Zn and 80 wt% Bi-Sn heated at 245 °C for 45 minutes produced a microstructure that showed Zn “islands” surrounded by a Bi-Sn matrix. Time dependent heating trials showed that Bi-Sn coalesced and coarsened with time, peaking at 50 minutes.Several coating compositions were tested for corrosion protection. Scanning Vibrating Electrode Technique (SVET) experiments showed that the addition of Zn to Bi-Sn made for a sustained galvanic protection throughout a 24 hour test. 20 wt%Zn and 30 wt% Zn exhibited the galvanic protection necessary, 10 wt% Zn showed instances of internal coupling.Open Circuit Potential (OCP) measurements showed that the novel Bi-Sn + Zn coating exhibited a lower OCP than that of steel, explaining the SVET results. Linear Polarisation Resistance showed low readings for polarisation resistance values, but comparable to other coatings in literature. Zero Resistance Ammetry confirmed SVET and OCP results, showing current flow from Bi-Sn + Zn coating to the steel substrate. However, the relationship between Bi-Sn and steel required further investigation and cathodic sweeps found that steel acts as a better cathode than Bi-Sn and explained the coating system’s protection of steel.Lifetime estimations are presented through calculations involving Zn volume and mass along with SVET – derived mass loss values. An estimated lifetime range of around 12-30 years is given.Mechanical properties such as adhesion and hardness were also investigated. It was shown that Zn addition had no effect on hardness. Adhesion testing showed that 20 wt% Zn / 80 wt% Bi-Sn offered good adhesion to the substrate under harsh bend test conditions with no cracking, flaking or delamination present.Near infrared (NIR) heating was explored as an alternative heating method to offer rapid curing of the novel coating. It was shown that 30% of the NIR power (up to 250 kWm-2) with a belt speed of 0.5 m/min offered the best microstructural results.Powers below 30% did not heat up to high enough temperatures and powers above 30% took the temperature of the sample too high.Fluxing was also investigated. Two fluxes, Zinc chloride and phosphoric acid flux, were compared for their wetting of Bi-Sn to a steel substrate. Zinc chloride showed superior wetting, owing to a thin layer of tin wetting to the steel surface. |
|---|---|
| Item Description: |
A selection of content is redacted or is partially redacted from this thesis to protect sensitive and personal information. |
| Keywords: |
Corrosion, Ground Support Equipment, Galvanic, Coatings, Corrosion Protection, Novel, Galvanising |
| College: |
Faculty of Science and Engineering |
| Funders: |
EPSRC, COATED2 |