In <list-1332123@skylee.com>, on 10/14/01
at 11:26 AM, "J. Forster" <jfor@onemain.com> said:
>wwd@netheaven.com wrote:
>> When the bubble forms on the metal surface, molecules of the metal are
>> 'sucked' off since the bubble is actually a vacuum.
>I very much doubt that metal is "sucked off" since the maximum negative
>pressure possible is 1 atmosphere. The compressive forces are almost
>unlimited, but tensile forces are not, foer this reason.
Well, you offer no explanation for the metal erosion. I'll expand my
description by saying that the bubbles are actually formed by the process
of boiling and the results are very corrosive. Take a boiling aluminum pot
of salt water. Once pitting of the surface begins, erosion proceeds
rapidly. Metal exposed to the 'steam vacuum' gets sloughed off, one way or
the other. And the prop is moving past water at a furious rate compared to
the boiling pot. One reason boaters pay good money for stainless steel
over aluminum props (Uncle Sam?).
Bill
-- ----------------------------------------------------------- wwd@netheaven.com -----------------------------------------------------------
This archive was generated by hypermail 2b29 : Fri Dec 07 2001 - 00:36:26 PST