What commonly available alloy has the best corrorsion resistance properties?

The 300 series stainless alloys would work fine, 316L is likely the best amongst them. It's readily available at a reasonable price, and easily fabricated.

Harold

How does Aluminium stand up against stainless steel? Also would it help protect the metal if I coated it with gold?

I'd be inclined to think aluminum would tend to reduce to the ore from which it came, assuming it got exposed to moisture. If not, it would likely stand up to time just fine. It forms a skin of aluminum oxide almost instantly when exposed to atmosphere, which protects it from further corrosion.

A surface finish of gold would certainly make it more resistant to corrosion, but you may not have the means to apply the gold. It's not as easy as you might imagine, due to the aluminum reducing the gold from solution, or the gold migrating into the aluminum after it has been applied, assuming you were successful in getting it that far. A protective barrier of nickel would probably have to be applied, then gold. It would likely be cheaper in the long run to use stainless, which would be resistant to corrosion from all atmospheric conditions, and would stand up better to fire----although unless it was well insulated, the contents of the chamber would be destroyed by heat. Aluminum, by contrast, would melt. In either case, you're not going to be protected against excessive heat, so you'll have to research proper insulation if that's a concern.

Harold

Purple plague, anyone? Aluminum and gold do strange things indeed.

Does he have to be heat resistant?

The other issue is for a chamber of that size, he could just as well use pure gold as the material as the cost would be inconsequential.

Oh wait, I meant to say, for a chamber of that size, his best bet would be concrete, as the cost for any metal would be prohibitive.

Hmm. Where in the center does the truth sit? It would be easier if he said he was making a box to put his DNA in, or if were buildign a bomb shelter to house his entire extended family.

Honestly concrete's not a bad choice. How about granite, seriously?

Fireproof, create a cavity inside a block, with a tight fitting lid and possibly some sort of gasket, put the lid on and there you are.

Worked for the pharos, eh? (though not with granite)

Jim

In 500 years it is unlikely to still be indoors. Bronze ship nails have survived 2000 years of salt water immersion so that is a good start.

Concrete.

It worked well for the Romans.

Cheers Trevor Jones

My first choice would be a 70/30 copper nickel alloy.

The cheapest hot-rolled crap you can find in a scrap yard, w/ about 5 coats of rustoleum+epoxy paint. Also, wall thickness will be directly proportional to longevity. 16 ga?

1/8? 1/4?? Could also go w/ plastic on a metal frame. 500 years, eh? Man, you must be takin one helluva vitamin....

If it will be indoors, what kind of "elements" do you expect to have to resist? Does it need to be fireproof? Earthquake resistant? How structurally sound does it have to be? How big?

If it's go> What commonly available alloy has the best corrorsion resistance > properties?

I would suggest going to a archaeological museum and looking at artifacts. Items made of copper seem to perform relatively well even after being buried. Stainless steel has not been around for long, but seems to be a [relatively] inexpensive, very slowly corroding material.

i

Monel is one of the best in the marine industry. It's very nobel.

According to James :

This sounds like a "time capsule". A quick web search found this page, which offers some suggestions -- including about things which you may not have considered:

Good Luck, DoN.

Yes, it is, and also VERY expensive. Stainless is a bargain by comparison.

Harold

The chamber is going to be around 6" in diameter and 12" in length, wall thickness is going to be 5mm. Its purpose is to hold data disks for long term storage. The chambers are going to be placed into fire safes and the safes will be placed into underground bunkers.

Would plating the Stainless with gold help prevent corrosion?

The chambers will be filled with nitrogen gas to help preserve the disks. What would you recommend for a seal? It cannot be any substance such as rubber due to outgassing. I need something that makes a good seal and does not deteroriate rapidly. The chambers will be opened periodically, around every 50 years to refresh the disk media.

Can you also recommend a good machine shop in the Phoenix, AZ area? I need a place that can weld all the pieces together.

Thank you for your help.

The problem with long term media storage is not deterioration but lack of playback hardware. I have lots of media from a mere 25 years ago that cannot be read, not because of deterioration but because no hardware is available. Try to find a punch card reader, a paper tape reader, a Sony PortaPak reel-to-reel video player, a Beta video player, a video disk player, a Polaroid film projector, an 8-track tape player, an 8 inch drive, a single-sided 5 1/4" Apple II drive, a CP/M single density Osborne drive, any number of tape drives, and so on.

Unless you are packing the hardware away with the media, deterioration is not going to be your problem...

Is this an art project? Or does someone actually expect to retrieve this data?

The retrieval concern is already taken care of. The data will be relevant for thousands of years as most knowledge is.

I would use a o-ring piston seal. You can get o-rings in various materials, but I suspect synthetic rubber ( Buna N ) will not outgass.

Dan

James wrote:

I do not see what the big deal is, your application is very forgiving. If you keep your stuff inside a copper pipe, with copper end caps, sealed with some kind of tar, it should last thousands of years. Your checks every 50 years will take care of any possible problems. Check out archaeology museums.

i

According to Emmo :

a punch card reader, Got it a paper tape reader, Got it a Sony PortaPak reel-to-reel video player, Never had a Beta video player, Got it a video disk player, Never had a Polaroid film projector, Never had (unless you mean a 35mm slide projector for their 35mm slide film) an 8-track tape player, Never had an 8 inch drive, Several a single-sided 5 1/4" Apple II drive, Had one -- gave it away to an Apple II user a CP/M single density Osborne drive, You mean the Shugart 5-1/4 single side single density -- Got em. any number of tape drives 9-track up to 1600 BPI 2-track and 4-track audio QIC-150 8mm DAT (both digital backup and audio)

, and so on.

Well ... a cheat sheet can be packed with the punch cards, so they can be read visually. :-)

For a while -- maybe -- but probably not necessary.

Teflon O-ring, perhaps?

Which means that you will need a standard fitting for backfiling with the inert gas each time.

Nope. That, I can't from Virginia.

Good Luck, DoN.