T1223-02 Wheelset Coating Systems and Good Practice Guidance

Descriptions

Coatings are necessary to provide corrosion protection for wheelsets and consequently to reduce the risk of generalised, or worse localised, material loss leading to mechanical failure of the component. If a coating even only partially delaminates from its substrate, it no longer fulfils its purpose. Therefore, it is crucial that the rail industry takes appropriate steps to improve the performance of coatings and identifies adhesion failures before they compromise the component integrity. Current specifications for overhaul procedure WOSS 612/10 will not allow overhauled axles to have any surface corrosion . However, thirteen NIRs have been reported since 2003 that relate to flaking, peeling or inadequate coating that has in some cases led to cracking. It is possible that there are many other unreported incidences. Some of these reports describe failures of the coating system that were not detected until the extent of corrosion of the substrate became significant. Lacking a coherent approach to the issue, the industry misses the opportunity to learn from cross-industry experience and past incidents. From the few incidents reported it has been difficult to pinpoint a single root cause for each case of coating delamination. At the same time, the reports identify several potential contributing factors that suggest steps to prevent the occurrence of unfavourable conditions in the first instance may be missing from procedures (for example appropriate coating storage, optimal substrate preparation). Similarly, opportunities to detect defects and repair them before coating delamination are often not exploited. It appears that the rail industry would benefit from documentation and information that clarify the necessary requirements for a suitable coating system to aid selection; and provide guidance on its application as well as maintenance and repair. This project aims to provide a clear and comprehensive understanding of coating systems for the rolling stock underframe environment, for both passenger and freight vehicles. This will reduce risks of failure, enable more accurate predictions of component life expectancy and allow a better planning of maintenance cycles. By developing a compendium of coating systems - including guidance on surface preparation, coating application, removal and maintenance - this research aims to enable the development of better-informed processes related to surface protection of wheelset components. Since Alstom's - acting as industry supporter for this project - current overhaul cycle ends in May 2021, there is an opportunity for the guidance developed by this project to be trialled during their next overhaul. RSSB will also evaluate with the relevant stakeholders the opportunity to feed the findings from this project into further work to generate a Guidance Note and to incorporate recommendations in IB/TS 0648 Data for Wheelset Overhaul and Repair and/or CR/PE 0102 Repainting of Rail Vehicles.