SDSS limitation

[Ein-no-stein]

Dear All,
As stated in ISO 21457, SDSS (25Cr) is limited to 90 to 110°C for marine atmospheric environment. The lower end of 90°C is probably based on the worst case situation at high tensile stresses and at concentrated chloride salt levels experienced when salt containing water is continuously evaporated. However, many operators use the higher temperature limits.
I am wondering if SDSS bolts (uncoated) is going to be used in marine environment. Do I need to consider the lower end or high end temperature?

Thanks for your opinion.

 

[SJones]

The table in ISO 21457 is entitled "Typical temperature limits...." Thus, they cannot be taken as definitive go - no go values. When performing a materials selection exercise like this, one has to establish a rational basis of justification. Your consideration of the temperature limitation should start with a review of published data in an attempt to support the application temperature of the equipment that you are considering. Some of the operators that you note may have justified the use of higher temperature limits based on their own testing programmes. Conversely, some operators have lower temperature limits - chloride stress corrosion cracking is not the only damage mechanism that will apply to fasteners in a marine atmosphere, as stated in the text of ISO 21457, 6.6.2.

The wishy washy text of 6.6.2 also states "Many end users have used the higher temperature limits indicated in Table 3. Extensive field experience over many years shows that very few SCC failures have occurred on uncoated and uninsulated pipes when these higher temperature limits were used." Will this statement relate also to fasteners? How lucky do you feel?

Try the following:

https://otk-sitecore-prod-v2-cdn.az...b5b-8e32-fbf8dc2111b5&modified=20171117090708

T Prosek, et al, Low Temperature Stress Corrosion Cracking Of Stainless Steels In The Atmosphere In The Presence Of Chloride Deposits, Corrosion, Vol 65, (2), 2009, pp 106 - 117

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.