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Do Ra values deteriorate with exposure to the elements
Q. Hi
I am a project manager on construction sites, at present I am involved in the installation of stainless steel handrails along a dock edge. The specification requires a satin finished stainless steel grade 316 finished to an Ra value of 0.5 or below. The current supplier believes that the Ra value will change as soon as the hand rail is installed and exposed to the elements. I do not accept this, can you advise if there is any evidence to support or refute this statement.
Regards, Len Burgess
Project Manager - UK
July 29, 2009
A. All surface finishes change with age and exposure to the elements speeds up that change. Without some kind of surface protection or sealing of the materials porosity, oxidation will reduce any material. Then again, the proper sequence is that the material is actually swelling before deteriorating.
AF Kenton
retired business owner - Hatboro, Pennsylvania
August 3, 2009
A. Hi. If the handrail doesn't corrode at all, the Ra would not change. If it does corrode, think about pits & rust, and the great effect they would have on Ra.
If the railings are electropolished 316 SS, I think they would resist rust for long enough to render the question moot over the time involved in installing the railing.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
July 2010
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