Albz Km

WPC exterior decking planks is suitable..

we can go with any material provided it is protected from causes of corrosion . ratan Kumar has already recommended automative paint. take care to avoid GP go for MS or GI with required thickness considering corrosion maintaining the stair is equally important

go with a fabricated stair in GP material and give an epoxy primer coat with automotive paint. please don't forget to clean off all the oil stains from the pipe before applying epoxy primer with any detergent as there is a chance of peel off after sometime due to weak bonding with the substrate in the presence of oil stains

GI / Stainless Steel . GI , weld ചെയ്യുന്ന ഭാഗം നല്ലവണ്ണം epoxy paint ചെയ്യാൻ മറക്കരുത്

or else build good metal stair using 2mm or above sections then maintain well

stainless steel n aluminium less corrosive

RCC