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Etch rate determination for a cylindrical object

I'm looking for a formula to determine the etch rate for a cylindrical sample of 15-5 Stainless Steel based on weight loss over a set period of time (15 minutes). This is for removal of just 0.0002 inches and the cylinder has some variability to its diameter so I'm reluctant to determine rate using micrometer measurement.

Jacob Hendrickson
Plating Shop - Seattle, Washington, USA
2004

For precise removal, immersion etch is more uniform than reverse current etch, though more messy. A mix of 60-40% ferric chloride [on eBay or Amazon] and nitric acid at room temperature will etch two tenths in approx. 15-20 seconds for 400 series SS. The mixture is so potent that only a plastic vessel is suitable. Irritant and toxic fumes dictate proper personnel protection. Disposal to comply with local regulations.

Guillermo Marrufo
Monterrey, NL, Mexico
2004

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Jacob,

The easiest way to do this is to obtain a sample of the alloy that is easily measured with a micrometer and run tests with it. Otherwise you need to determine as precisely as possible the surface area of the cylinder and weight before etching. Using .285 lbs/cubic inch as the density of 15-5PH you can calculate the etch rate in tenths or whatever unit you desire.

Tim Hamlett, CEF
- West Palm Beach, Florida, USA
2004