What is the best type of grating to use at a wastewater treatment plant? I have always specified aluminum. The Owner is wanting stainless steel and has even mentioned some type of plastic coated steel.
Plastic coated steel is dangerous. It is not obvious whether the steel is rusted or not, which could happen if the plastic is perforated. I have had one instance of a plastic coated steel ladder disintegrate under someone when they were using it. The ladder looked fine, it was just plastic coated rust.
Some years ago, I worked on a mobile unit for hazardous waste treatment. All the surfaces that we had to walk on were fabricated of this wonderful green fiberglass grating. It was fashioned such that the edges of the grate material that faced upwards were concave, and were...sharp, if that makes any sense. They gripped the rubber sole of one's shoe wonderfully.
Though we worked under perpetually wet conditions, with lots of slippery stuff around, no one ever slipped. And, this stuff never broke. I wish I knew what it was called, so I could recommend it by name.
Most WWTW in Oz use FRP gratings especially if they are near the ocean (most are) & subject to WW gas degradation.
Bit expensive tho.
It depends on the proximity to WW gas production. If there are reasons for access away from the problem areas, galvanised steel is generally used (replacement every ten years is MUCH cheaper than using aluminium or FRP).
Press locked or swaged aluminum grating has been a problem. It rends to feel insecure even if design properly. The deflection is more than is comfortable and the grating tends to shift slightly from side to side because of a lack os stiffness. Truss-locked or aluminum plank style is preferred.