Posted by Dan Shockley on Tuesday, October 30, 2001 at 4:01PM :
In Reply to: Stainless steel fasteners-questions posted by Galen on Tuesday, October 30, 2001 at 11:32AM :
Okay, it is my turn to add my two-cents. There are three types of stainless steel: austenitic, martensitic and ferritic. These three types are based on the microstructure present. Austenitic is the non-magneic variety, it has the best corrosion resistance, and is also the most expensive. Both martensitic and ferritic stainlesses are magnetic and can corrode under normal circumstances(such as in an inner fenderwell application).
The following rankings are from greatest to least and I am using the First letter of each of the three types as an abreviation. These are general trends and are from memory so they are correct to the best of my knowledge and I am aware of exceptions.
Strength M,A,F
Ductility A,F,M
Corrosion A,F,M
Cost A,M,F
Fatigue life M,F,A
The last one is the kicker when it comes to stainless fasteners. In order to get the best corrosion resitance and adequate strength, you just give up fatique resistance. In most applications mentioned in this thread, this won't be a problem, however, there are times when this can be a serious problem.
Case and Point: In the last few years several multi-size trailer balls have come to the market with interchangable balls. One of the suppliers sells stainless versions of their hitch ball. When used for long duraions at any where near the rated capacity, these fail. I had the opportunity to examine one such failure. It occured at well below the rated capacity.
When converting to stainless fasenters, I would recommend only doing so in areas not sensitive to load, such as, body fasteners, trim, accesories and other items. Do not use these fasteners were a failure could result in a accident, or major component failure.
Just my two cents worth, good luck on all your projects,
Ferrously yours,
Dan Shockley
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