Q: I’m using sodium hypochlorite to control slime and bacteria formation in a power plant water system. It’s in about a 15% solution. I tried using Duplex fasteners thinking they are good with chlorides but I’m having corrosion issues. Any suggestions?

A:  I think the problem you have is the fact that sodium hypochlorite is a strong oxidizer. Duplex can experience corrosion in chloride solutions where oxidizers are present. In this case, I would suggest either Titanium grade 2 or grade 5 depending on the level of strength you need. Both titanium grades are nearly immune to hypochlorites. Titanium provides excellent resistance to oxidizers because of its stable oxide film, which regenerates almost instantly in the presence of water or oxygen. Both grade 2 or 5 will exhibit these properties. Grade 5 is only necessary if you require higher strength.

Q: I’m working on a on a geothermal energy drilling project. Carbon steel we’re currently using to bolt drilling components is failing from corrosion. We have corrosive an environment with high levels of sulfur and salt, as well as temperatures to 260C. Any suggestions?

A: Super Duplex 2507 is often used in geothermal explorations. It is a steel alloy that contains chromium, molybdenum, and nickel which greatly improves its strength, corrosion resistance and temperature capabilities compared to most carbon steels. Super Duplex 2507 fasteners are known to provide very high resistance to pitting, erosion and crevice corrosion, as well as corrosion fatigue and stress corrosion cracking (SCC) in chloride environments.  Also, Super Duplex fasteners have good general corrosion resistance to moderately acidic environments. Not knowing your exact conditions Super Duplex is certainly worth looking into more as well as other higher performing alloys like Inconel or Hastelloy, which are known to handle  hot concentrated solutions of sulfuric acid much better.