Corrosion Resistant Bolts for Submerged Applications

[Zehavi]

I need to find out where I can obtain corrosion resistant bolts or coatings for bolts. This is my problem: I am installing bolts in a handrail which is being bolted to concrete. The bolts are installed inn water with a fairly high chlorine content. So far, the bolts we have tried have failed. LOTS of rust!

What can I do?

Avi Nachshoni

 

[TVP]

Depending on the strength requirement, as well as the chloride concentration, you may be able to use conventional stainless steel fastener alloys. The following document from SSINA is an excellent reference with which to start:

http://www.ssina.com/SSINA2002/SSINAsite/publications/fasten.html

Fore more information on advanced alloys, I recommend you read the following article on multiphase fastener alloys from SPS:

http://www.spstech.com/aero/news/090602.html

They also have an excellent booklet on these alloys called Superalloys Developed by SPS Technologies for Aerospace Fasteners which you can obtain by clicking on the following link:

http://www.spstech.com/aero/prod_lit/index.html

The following technical article on the AvestaPolarit website on bolt performance in seawater that may be useful:

http://www.avestapolarit.com/upload/documents/technical/acom/acom93_1.pdf

And lastly, the November issue of Advanced Materials & Processes (

http://www.asminternational.org/Template.cfm?Section=Magazines&NavMenuID=701)

featured an article on Inconel 686 for marine fasteners. More information is available from Special Metals using the following link:

http://www.specialmetals.com/publication/tech_bulletin_686.pdf

 

[kenvlach]

What is the handrail material and its finish?

 

[SJones]

What bolting material failed in the first instance ? If the bolting is in the splash zone, or intertidal zone, and will be subject to wave action, Inconel 625 should be considered. As a rule of thumb, when selecting stainless steel or nickel alloys, the pitting resistance equivalent number (PREN) given by %Cr + 3.3 x %Mo + 16 x %N should be higher than 40. What is the handrail material as you may need to watch for galvanic interaction ? Do not use any sulphide containing lubricants.

 

[JimMetalsCeramics]

Provided they meet your strength requirements, titanium bolts are used in chlorinated environments.