The RHA is made entirely of A316 stainless steel (with the exception of the teflon coated phosphor bronze DU bearings). A316 is one the highest corrosion resistant (stainless) steel alloys available and is commonly used in marine and sterile laboratory applications.
I chose 316 because of its non corrosive properties given where it is installed, ie. right in line with of the road crud and rain water thrown off the back wheel. The manufacturers were not too happy about this as A316 stainless is very hard and difficult to cut.
What distinguishes Type 316 from the more common Type 304 is the addition of molybdenum up to a maximum of 3%. Molybdenum increases the corrosion resistance of this chromium-nickel alloy to withstand attack by many industrial chemicals and solvents, and, in particular, inhibits pitting caused by chlorides. As such, molybdenum is one of the single most useful alloying additives in the fight against corrosion. By virtue of the molybdenum addition, Type 316 can withstand corrosive attack by sodium and calcium brines, hypochlorite solutions, phosphoric acid; and the sulfite liquors and sulfurous acids used in the paper pulp industry. This alloy, therefore, is specified for industrial equipment which handles the corrosive process used to produce inks, rayons, photographic chemicals, paper, textiles, bleaches, and rubber. Type 316 is also used extensively for surgical implants within the hostile environment of the body.
Analysis of Stainless Type 316: