Re: RE: [PSUBS-MAILIST] protecting Aluminum parts

[Bob Duncan <katsurencho@yahoo.com>]

Yes, i believe it is 7075 T-6 that is used in high pressure tubing, often in place of stainless steel. Fluid pressures of 3000 to 5000 psi.

 

bob

jbarlow@bjservices.ca wrote:

No, not marine industry. Internal pipeline inspection. I use 7075 for its
higher strength over 6061 where non magnetic material is req'd and weight
is a problem letting out stainless steels. Anodizing seems to protect the
aluminium rather well from corrosion. Our tools are sometimes run for up
to a week in a sea water pipeline, and may spend up to a month on an off
shore platform which seems to eat many materials but the aluminium, if
anodized, seems ok. Admittedly, corrosion resistance is not my primary
concern.



Jay.







Bob Duncan
To: personal_submersibles@psubs.org
Sent by: cc:
owner-personal_submersible Subject: Re: RE: [PSUBS-MAILIST] protecting Aluminum parts
s@psubs.org


2004-01-13 13:44
Please respond to
personal_submersibles






Are you using 7075 in the marine industry? It would seem to be excessively
acceptable to corrosion.

bob duncan

jbarlow@bjservices.ca wrote:

Getting the parts Hard Coat anodized provides aprox 60 HRc surface of
Aluminum oxide (similar to its natural oxide) but is quite impervious to
scratches ect. It also makes the surface not conductive thus preventing
galvanic corrosion. I believe the correct call out is "Type III Hard Coat
Anodize" I usually get 6061-T6 parts anodized, but have anodized 5052 and
7075 grades as well.


My 2¢.

Jay.





drewacard@charter.net
Sent by: To:
owner-personal_submersible cc:
s@psubs.org Subject: Re: RE: [PSUBS-MAILIST] protecting aluminum parts


2004-01-07 07:47
Please respond to
personal_submersibles






6061 is a marine grade if it is harden to T6 hardness it will form a thin
oxide layer on it own. This thin layer will protect the metal from salt
water if it is not scratched. However I would coat the ring with a clear
epoxy or polyester paint to prevent galvanic corrosion

just my 2 cents
Andy Jensen

From: "Alec Smyth"
Date: 2004/01/06 Tue AM 09:52:50 CST
To:
Subject: RE: [PSUBS-MAILIST] protecting aluminum parts

Its 6061.

Thanks,

Alec

-----Original Message-----
From: drewacard@charter.net [mailto:drewacard@charter.net]
Sent: Tuesday, January 06, 2004 9::50 AM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] protecting aluminum parts

What grade of Aluminum is it?

From: "Alec Smyth"
Date: 2004/01/06 Tue AM 08:14:08 CST
To:
Subject: [PSUBS-MAILIST] protecting aluminum parts

One of the relatively more expensive parts of my sub is a massive
aluminum ring that seats the acrylic bow dome and opens and closes as a
hatch. I know it will form an electrolytic pair with other metals on the
boat, and thus corrode. But I have a practical question... given the sub
is likely to be in the water only an hour or two, and get washed down
with fresh water afterwards, is the need to protect the aluminum real,
or would it only be an issue with longer exposures?

I'd be much obliged if anyone with unprotected Al parts on their sub
share their experience on this. Anoziding looks nice but on a part this
size would be very expensive (extrapolating from what I've paid for much
smaller parts, probably in the order of $500). I'm not sure whether to:

a) Do nothing
b) Use a zinc anode near the hatch
c) Paint
d) Anodize

Just as background information, I don't have any other metals in direct
contact with the Al on the wet side, except for the hatch seat, but that
should be pretty well protected as it has 4 coats of Gluvit epoxy base
and 5 coats of epoxy paint. On the dry side, the ring is mechanically
connected to bars that go through linear bearings attached to the hull.
This does connect it electrically to the hull as well.

Thanks,

Alec








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******************************************
* This e-mail was virus scanned when sent.
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Two guiding principles govern Israel Naval Commando doctrine:

1.Every defense system is vulnerable.

2.The enemy can deal with weapons and operational methods that are known; for that reason, naval commandos use imagination, daring and initiative, to create situations which cannot be anticipated.

---

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