Can I use stainless steel cable ties on hot dip galvanised cable tray?

Might be worth speaking to the manufacture of the hot dip galvanised tray and ask them do they have the same material for cable clips?  Normally it is better to use the same material for the tray and clip as this will reduce corrosion depending on the enviroment.  GRP tray may also be another option have a look at marshall-tufflex (other brands are available)

www.marshall-tufflex.com/.../

GRP tray may also be another option

Given that the use of metal ties is usually driven by the need to prevent premature collapse in the case of fire, selecting a plastic tray might be a bit counter productive?

   - Andy.

Worth having a look at 

https://www.marshall-tufflex.com/case-study/grp-trunking-keeps-rail-station-renovations-on-track/

They state

GRP is the material of choice for a wide range of cable management projects in the rail network. The robust product is specifically designed for challenging environments with the material effective at temperatures from -80°C to over 130°C. It is both corrosion and fire resistant with low thermal conductivity and self-extinguishing properties that make it fully compliant with fire standards and regulations

Sergio Fernandez said:

at temperatures from -80°C to over 130°C.

Most building fires produce temperatures way above 130 degrees, fire resistant and self-extinguishing aren't the same as being able to support cables during a fire. Compliance with standards isn't the same as meeting specific requirements. People still sell PVC conduit and trunking, but they won't meet the requirements of 521.10.202 without the addition of fire clips or steel saddles fixed into a solid substrate.

  - Andy.

Sergio Fernandez said:

at temperatures from -80°C to over 130°C.

Most building fires produce temperatures way above 130 degrees, fire resistant and self-extinguishing aren't the same as being able to support cables during a fire. Compliance with standards isn't the same as meeting specific requirements. People still sell PVC conduit and trunking, but they won't meet the requirements of 521.10.202 without the addition of fire clips or steel saddles fixed into a solid substrate.

  - Andy.