Galvanized steel cable tray is the right answer almost everywhere, until it is not. Take it into a chlor-alkali plant, onto a coastal jetty, into a fertiliser unit or an effluent hall, and the zinc that protects it everywhere else gets stripped in months. We once inspected a two-year-old hot-dip galvanized run above a pickling line that had lost most of its coating to acid fume and was rusting along every cut edge. On those projects the question is not which steel. It is whether steel at all. Three materials compete for corrosive and coastal work: hot-dip galvanized steel, stainless steel, and FRP. Each one wins somewhere and loses somewhere.
Hot-dip galvanized steel, and where its limit is
HDG is strong, cheap for its strength, easy to earth, and good for 25 years in ordinary industrial and outdoor air. Its weak point is chemistry. Zinc is attacked quickly below about pH 6 and above about pH 12, so acid fume, alkaline splash and chlorine eat it. Salt air speeds the whole process up. In those places HDG still has a role for short-life or easily replaced runs, but specifying it for a 25 year design life beside the sea or over a chemical line is wishful thinking. If you must use it there, go to a heavier coating and accept that it becomes a maintenance item, not a fit-and-forget one.
Stainless steel, when you need strength and chemistry both
Stainless gives you the load capacity and the earthing behaviour of steel with far better corrosion resistance. The grade matters more than the word stainless. 304 handles general corrosive, food and pharma environments. 316 and 316L, with added molybdenum, are the grades for coastal salt and many chemicals, which is why offshore and marine specifications call for 316 almost by default. It is the dearest of the three on metal cost, but it carries heavy power cable, holds its strength in a fire, and lasts decades where zinc is gone in a year or two. For a critical run you cannot easily get back to, the metal premium is small against the cost of a shutdown.
FRP, when the environment beats all metal
Fibreglass-reinforced plastic, also called GRP, is a non-metallic tray moulded from glass fibre and resin. It does not corrode at all in acids, alkalis, salt or effluent, it is light to handle, and it does not conduct, which is a safety advantage in some layouts and a complication in others. The trade-offs are real. It carries less load than steel for the same section, it needs closer supports because it deflects and can creep under sustained load and heat, the resin sets a temperature ceiling, and because it does not conduct you must run a separate earth conductor instead of using the tray as a parallel earth path. Match the resin system to the specific chemistry, vinyl ester for the aggressive acids, and confirm the fire rating for the location.
A quick way to choose
- Ordinary indoor, outdoor or industrial air: hot-dip galvanized steel. Do not pay for stainless where zinc lasts 25 years on its own.
- Coastal, marine or offshore, within a couple of kilometres of salt: 316 stainless, or FRP where the load is light and weight matters.
- Acid or alkaline fume, chlor-alkali, fertiliser, effluent: FRP with the right resin, or 316 where load and fire demand metal.
- Food, pharma and clean process: 304 or 316 stainless for washdown and hygiene.
- Fire-risk escape routes: steel, because the resin in standard FRP has a temperature limit, unless a tested fire-rated FRP is specified.
Do not forget the earthing decision
This is what catches people out. A steel or stainless tray can act as a parallel earth conductor when its joints are bonded, so the tray itself becomes part of the earthing system. An FRP tray cannot, because it does not conduct, so every FRP run needs a dedicated earth conductor sized and clipped along it. Settle this at design stage, not on site, because adding an earth conductor to a finished FRP run is slow work and a missing earth is a safety finding waiting for the inspector. Whichever material you pick, the accessories and supports have to match it, the same finish-matching rule that governs every tray system.
The material question on a corrosive project is settled by the chemistry and the load, not the price per metre. Galvanized where zinc survives, 316 where salt and load meet, FRP where the environment beats all metal, and always decide the earth path before you order.
Specifying cable tray for a coastal, marine or chemical plant? We manufacture hot-dip galvanized and 304 or 316 stainless ladder, perforated and trunking systems with matched accessories and supports, and we advise on the earthing path for the material you choose.