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Stainless steel water markers won't stay polished

2002

I am an architect working on a new water intake structure in a highly visible area of the Sacramento River. We've embedded multiple type 316 stainless steel water markers flush to the concrete structure. We've ground them to a fairly reflective polish twice now, only to have them (oxidize?) turn gray as concrete almost uniformly after a rain.

Is there a way to keep this stainless steel reflective w/o constant polishing? Are we using the wrong sandpaper? Is there a chemical to both remove the gray film and maintain the polish?

Thank you,

Jason Ellis, Senior Designer
- Sacramento, California, USA

As long as you keep grinding, the parts will keep corroding. What you need to do, is have the parts passivated to produce a finish that will be resistant to the water. Passivating will leave an oxide-rich layer that is more resistant to the attack of the water than the iron-rich surface that is created by grinding. You may also look at electropolishing to accomplish this.

Dan Brewer
chemical process supplier - Gurnee, Illinois
2002