What about using 316L? We use it widely at sea. Yes, it can still corrode, but needs to be a REALLY harsh environment to do anything other than tarnish the surface.
The requirement to prevent static build up on plastic surfaces/coverings and possible solutions/mitigation is all described in BSEN 60079-14 Para 6.5.
General thought process is to reduce the surface area of any cable support system, so install ladder rather than tray, if plastic covered ladder/tray is used then insulation resistance properties if below 1GOhm then static will dissapate naturally.
Other thing to think about is, what is the hazradous/flammable material, remember the installation must be suitable for the environment and yes plastic/fibre glass may deal with any corrosive nature the material has on steel containment, but what you dont want is the material turning your plastic covered tray of fibreglass tray all gooey after a few years or it getten softened it looses its mechanical strength.
Is Stainless steel a possible option for you?