most corrsion resistent metals

:bugeye: i tried a simple search and nothing came up.. so i'm posting..please excuse the sciforum noobness

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I'm currently experimenting with small scale hydrogen cells.. useing what i could find from local stores... I was told stainless steel would be resistant enough to use long term..after several attempts, distilled water filtered and distilled etc.
Diffrent strengths of electolytes. currently sodium bicarbonate (baking soda)
varying voltage vs production..


The "stainless steel" i've been using is rendered useless within seconds.. turning the water a mess of grey chunks and green, brown hues.. obviously copper/tin and probably lead, iron content of the metals used..

So if i were working with a $20 investment on a material that would stay together even in hot acid.. what would i buy? I've heard platnum and iridium are highly resistent to corrsion.. but are probably gonna be out of my price range as well as others.. maybe i got the wrong type of steel...

 

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Stainless steel is a pretty broad term in itself..
Try and get your hands on a Machinery Handbook and
also Carpenter metal<doesn't make sense does it

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>
has pretty extensive product specs. website
http://www.cartech.com/

 

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You probably did get the wrong type.
The last time I worked on a hydrogen cell it WAS stainless steel and contained an oxygen/ hydrogen mix at ~300 degrees C and something like 15 atmospheres.
And no hint of corrosion.

 

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I did a simple search and found this:

Tantalum

Tantalum owes its corrosion resistance to a tenaciously adherent oxide film akin to the entire family of passive, reactive metals. The metal has gained acceptance for use in electronics, missile technology, the chemical industry and the medical field. Tantalum is immune to attack by many acids and salt solutions. It is, however, subject to hydrogen embrittlement in alkaline solutions. It is used to fabricate heat exchangers, reaction vessels, bayonet heaters, thermo wells, surgical implants and radiation shielding. Tantalum should not be used in air at temperatures above about 300°C because of severe oxidation.


Niobium

Niobium, as with other reactive metals, owes its corrosion resistance to a passive, tenaciously adherent oxide film. The corrosion properties of niobium are similar to those of its sister element tantalum, however, it is less resistant to more aggressive media. Unlike the other reactive metals, niobium will tolerate the presence of small amounts of fluoride ion. Niobium and its sister tantalum can become embrittled with hydrogen in alkaline service, however, it is one of the few materials that are resistant to aqua regia. The oxidation rate of niobium in air increases with temperature and becomes quite rapid above 500°C. Therefore, when niobium is used at higher temperatures, coatings must be employed to minimize detrimental oxidation. Applications include missiles and aerospace because of strength at elevated temperature and the chemical industry due to its corrosion resistance. It is also resistant to many liquid metals.


Zirconium

Zirconium is a reactive metal that owes its corrosion resistance to the formation of a chemically inert, tenaciously adherent oxide film. As such, zirconium exhibits excellent resistance to corrosion in most organic and inorganic solutions. It is particularly resistant to reducing acids and strong alkalis. It is also resistant to strong nitric acid, some molten salts and is used in heat exchangers, valves, piping, reactor vessels, tanks, pumps, tower packing and laboratory equipment. Zirconium is our most effective crucible material for fusions using sodium carbonate, or sodium peroxide. It is an excellent low-cost replacement for platinum. And, based on an average of 100 fusions per crucible, it is more cost effective than less expensive porcelain or steel crucibles. The major use of zirconium remains in the nuclear reactor arena. The thermal neutron capture cross-section is extremely low so the metal acts as a window to these particles. It also exhibits good corrosion resistance to the aqueous media within the operational nuclear reactor.

Vanadium

Vanadium is a reactive metal; a sister element to niobium and tantalum. It has many attractive properties like low fusion neutron capture cross-section, low rate of neutron embrittlement, good corrosion resistance and a relatively low density. The inelastic-scattering cross-section is quite small, but the thermal neutron cross-section is large and its usefulness in thermal reactors is, therefore, limited. Vanadium is resistant to salt water, dilute hydrochloric acid and sodium hydroxide solutions. The resistance to molten lithium is excellent.

Titanium

Titanium is a reactive metal that owes its corrosion resistance to the formation of a tenaciously adherent oxide film. This film, unlike the film formed on its sister element zirconium, is conditional and can be enhanced by the presence of oxidizing ions in contact with the metal. It is resistant to most dilute acids and is excellent in sea water and brackish waters. Titanium has a high strength to weight ratio which dictates many of its more important applications in the aerospace industry. However, it is also used in the chemical industry in heat exchangers, the pulp and paper industry, tanks, piping systems, valves and pumps.

Nickel

Nickel belongs to the iron-cobalt group of metals. It forms an adherent oxide film that provides its corrosion resistance up to temperatures around 600°C. It’s highly resistant to alkalis and most acids, however, it is attacked by oxidizing acids like nitric and salt solutions containing oxidizing species. Nickel finds applications in the electronic and aerospace industries and in chemical and food equipment construction. Heat shields, evaporators, laboratory equipment, and glass to metal and ceramic to metal seals are additional applications that use pure nickel.


Inconel®

Inconel® is a nickel-chromium-iron alloy formulated to provide corrosion resistance and oxidation resistance at elevated temperatures. It has excellent oxidation resistance in the 1000°C to 1200°C temperature range and exhibits good corrosion resistance to many acids and aqueous salt solutions. Applications include thermal processing, the chemical industry, pollution control, aerospace, power generation and laboratory equipment.

Molybdenum

Molybdenum is a sister element to tungsten and is resistant to corrosion by many acids including sulfuric, hydrochloric, hydrofluoric, organic acids and many molten materials such as metals and glasses. It is, however, attacked by alkalis if oxidants are present. The metal exhibits good strength at elevated temperatures, but will begin oxidizing in air above 400°C with rapid oxidation above 600°C. The product of oxidation will sublime at temperatures over 700°C. ​

 

Titanium isn't much good for a home-build project: it reacts badly to chrome* steels - hence the reason for so-called "feather bedding" on certain tools bought by the USAF.
EVERY single tool used on servicing and maintaining the SR-71 had to be especially manufactured and bought for that aircraft.
Titanium's expensive enough without having to buy a complete new set of tools for tightening the nuts that hold the project together.

* Edit: actually it's probably molybdenum that it reacts badly to: most spanners (wrenches?) are cro-moly rather than just chrome steel.

 

You can use standard tools. Two different metals will usually react with each other when in direct contact. It's called galvanic corrosion. Are you sure you should be messing with this stuff?

 

Not from what I've read: complete wing panels had to be replaced because of a continued reaction after some bozo used his spanner on an SR-71.
Maybe that was just the then-current alloy in use...

 

Corrosion resistant high strength low alloy steels

ASTM A242 - structural shapes and plates
ASTM A588 - structural shapes and plates

 

Speaking of corten, Corten steel quickly develops a layer of corrosion, but that layer protects the steel underneath.

 

it seemed as good a name as any to pick.