Tag: AL6XN bolts for chloride resistance

Titanium Screws and Chlorides

Q: I’m dealing with a moderate chloride environment but my temperature can sometimes reach 450F. I’ve tried titanium bolts but am having some corrosion issues. Is there another material I can use?

A: There are several potential choices but as the temperature increases the corrosion rate and aggressive nature of the chlorides will certainly increase as well. While fasteners made from Duplex 2507 and AL6XN offer good corrosion resistance, high strength and perform well at 450F with chlorides a better route may be to go with Hastelloy C276 bolts. Hastelloy C276 bolts, will certainly give you a boost in corrosion resistance and minimize the effects of the chlorides. The NACE MR0175 version of the Hastelloy C276 will also be more resistant to stress corrosion cracking if your problem is stemming from this issue as well. .

Duplex Bolt Corrosion

Q:  I need some bolting to attach some surface steam piping for a power industry project. They’re using duplex bolts now but its showing some slight corrosion. Chlorides are involved and maybe some other contaminants. Ideas?
A:  Surface steam condensers and other power industry elements that are exposed to salts and chlorides often use AL6XN fasteners which offer a step up in chloride resistance from Super Duplex 2507 steels. Though AL6XN bolts will improve upon corrosion protection it is slightly less strong offering 53ksi vs 82ksi yield strength. If higher yield is needed to match the Duplex bolts, I would then suggest you use Monel K500 (110ksi yield). While AL6XN will be you most economic choice, Monel bolts will give you even further improvement on chloride resistance and higher strength.