I am currently looking for a lightweight material that is weather resistant for use as a cover plate for use on access hatches to box girders on bridges and viaducts. The plate is to be approximately 1.02m x 0.72m and 9mm thick. I would like this plate to weigh between 20 and 40kg and be resistant to all forms of corrosion including galvanic corrosion (the box girder is made from S355 mild steel). The plate will not be under any significant loading. I am reluctant to consider aluminium for this purpose as it is particularly susceptible to galvanic corrosion. I am wondering whether you can suggest any suitable materials? Any help would be much appreciated.
Stainless steel copper or brass
You may want to investigate fiber reinforced plastic which has been used as hatch and access covers. You may want to consider a vinylester which is fire resistant. This material is often used in chemical and food processing plants.
As soon as you stick different metals together, galvanic corrosion is a big concern. I assume the thickness of this part is determined by the loads it will be subject to?? If you use a higher strength material,the thickness can be less. One answer suggesting a material other than metal is a good suggestion. If the loads are low, you do not need strength. Plastics have some issues holding up in direct sunlight and the CTE of most polymer materials is high.