Re: [PSUBS-MAILIST] protecting aluminum parts

[MerlinSub@t-online.de (Carsten Standfuss)]

Polishing will reduce the surface area to a minimum - and a fine new
layer of oxide will cover the aluminium very quick - but I agree
polishing is more common for stainless steel than for aluminium. In
general we cover our aluminium motoryachts with zinc anodes in seawater
and with magnesium anodes in river- or lake water. And with a multi
-layer of epoxi-paints. 

If we paint a hull we ever use an special aluminium acid primer on a
fresh grinded or better blast aluminium hull - a normal metal primer
will give to quick way. 

Most problems we have with aluminium hull are in the area of the
propellers which are normaly make out of bronze. 
Even aluminium ships laying on a steel harbour key for longer times
can capture big troubles - special on the wall side. 

I like the idear of a transparent cover of paint or epoxi. Special in a
area near a arclic-dome.. (repaint without outbuilding the dome..)

A Psub will normaly only in water for hours - so corrosion should be not
a such big deal. 

Carsten

Adam Lawrence schrieb:
> 
> Oxygen accelerates corrosion attack, and the corrosion rate goes into orbit
> under higher atmospheric pressures. Polishing the part would have removed
> the passive oxide film at the surface, giving the oxidizing agent (sea
> water) a fresh start. 316 has higher Ni and Mo making it a better choice
> then 304.
> 
> Adam
> 
> ----- Original Message -----
> From: <VBra676539@aol.com>
> 
> > Hmmm. Maybe one of our metal guys will take a shot at that. The only thing
> I
> > ever did similar was replace a piece of 304 stainless in the oxygen system
> on
> > one of the boats when it turned to rust on a single dive. It should have
> been
> > 316 to start with, but we were all surprised that it rusted like that. I
> > wonder if we could have polished it out and by doing so, sealed the pores
> and maybe
> > made it shinier and less likely to do it again? Very strange. Vance