Stainless steel bolts vs. fertilizer vs. sea water 3

[Garvin]

Hi.

I have been involved in a project regarding loading of fertilizer onto ships. It is heavy duty equipment with an estimated total weight of 350.000kg.
The fertilizer most likely contains chloride and I'm kind of worried with respect to SCC in all those stainless steel bolts they are using. (Bolts in high tension)
I've been looking high and low, but have not been able to find any articles, reports or people that could really enlighten me.

What I'm most in doubt about is the combination of chloride, sea water/vapour and the ambient temperatures. Those articles that I have found allmost all says that the problem is worst at high temp's, but... some of them also says that it may happen at lower temp's ???

Is there anyone here that may have some advice, or is able to point me to some kind of documentation. Preferrably online for the time being, until I know a little more about it.

Your help/advice would be most appreciated.

Best regards,
Jan L

 

[metengr]

To help answer your question, What is your specific grade of stainless steel fastener?

 

[Garvin]

Actually they/I don't know yet, as they haven't decided anything else than it should be "standard" stainless steel fasteners...

I can find out sometime tommorrow, as I'm not at work right now.


Best regards,
Jan L

 

[mcguire]

Any martensitic stainless has its maximum susceptibility at ambient temperatures. Stay far away from them. Ferritics are too soft for bolts. A very stable austenitic PH with high strength like A-286 would resist ambient SCC. You could get 700MPa yield strength. Consider a duplex like 2507 if a yield strength of 550 MPa is acceptable. It won't SCC uder these conditions. After these you're looking at nickel base alloys or titanium.

 

[Garvin]

Thank you for your replies...
Do you happen to know if there are any good online articles regarding this particular or some similar subject?

My problem is, that I most likely will need some kind of "proof" to convince my boss/colleagues, that they may have a problem...


Best regards,
Jan L

 

[mcguire]

Try "Corrosion of Stainless Steels" by Sedriks, publisher Wiley. It leaves a lot to be desired but it's probably good enough for bosses.

 

[EdStainless]

I would suggest using either a duplex stainless or a PH grade in the overaged condition.
There are some good articles about near-ambiant temperature CSCC on the NiDI site, but I couldn't find the exact ones this morning. There have been failures of 304 and 316 in structural applications. The last one that comes to mind was the roof over a public swimming pool that failed.
Your main source of chorides will be from the sea fog each night. There is published data on how much choride you get, but it is enough to be concerned about.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[corrosionman]

And of course if you have stainless bolts to join structural steelwork in damp conditions, you will need to insulate joints to prevent dis-similar metal corrosion.
Cheers D W

 

[Garvin]

I thank you all for your input, and this thread alone was actually enough to make my boss take my concerns seriously.
We will now contact some experts, in order to get their recommendations for this particular task, as I unfortunately don’t have the resources to do it myself for the time being.

Thanks again...

Best regards,
Jan L

 

[EdStainless]

I am glad that you were able to present this to your boss. That shows that you have some pretty good skills.
The bigest step of any problem isn't defining hte problem, but getting people to understand that there may be one.
Such advice is what a number of us do for a living of as a sideline.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[Paskenell]

http://www.stainless-steel-world.net/pdf/11003.pdf

This might also be helpful besides what is mentioned above.

 

[SJones]

http://www.marinecorrosionforum.org/

Search term "bolting" will throw up some good info. One thing about lubricants: avoid MoS2-containing lubricants as they can decompose to give H2S which gives another form of cracking.

Steve Jones
Petroleum Development Oman LLC
Muscat
Sultanate Of Oman

 

[Garvin]

Thanks a lot... That was a very informative link.



Best regards,
Jan L