Q: I’m running a semiconductor wet chemical etching process that utilizes 85 % phosphoric acid at around 150-160°C. I need a material that can withstand this process. Super Duplex hex bolts are not cutting it.
A: At that particular concentration and temperature high performance nickel alloys like Hastelloy C276 bolts as well as Zirconium fasteners will have a corrosion rate most likely greater than 25 mils/year (0.025″/yr). The only metal that is commercially available in the form of fasteners and will not have any corrosion rate is Tantalum. Furthermore for semiconductor processing tantalum has an advantage of not contaminating sensitive materials because of its high level of inertness. However tantalum fasteners are not that strong so the mechanical requirements of the application need to be considered as well.