Stainless Steel, how bad is it?

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liveforphysics

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Hi guys, I am playing with the proto-type designs for my DIY wavemakers (they share the all good atributes of the vortech units, plus some bonus features ;)).

Anyways, while dorking around with the prototypes, it would sure be a lot nicer to get to work with stainless steel rather than Ti. Ti is such a PITA to work with, espically when you are frequently changeing things as you dial in the design. It welds like crap, and it cuts like crap, and its a pain to bend, and it chips carbide like there's no tomarrow. Its just nasty stuff, If i could get by with stainless for testing units it would really be a lot easier and cheaper for me.

So, I have been read the riot act about useing any metals besides Ti in the aquarium by just about everybody and there neighbor. However, I cant seem to think why stainless steel would be bad.

Its basically iron and nickel, and the nickel shouldn't be reacting with anything, so I guess that leaves the iron as the reason stainless steel is bad? Is this iron going to be something beyond what a thriving cheato mass will beable to safely bind, or is haveing some stainless steel parts in the tank going to cause wild zooanthale growth and cause corals to brown and yadda yadda?

Also, i dont know if anyone will have and experience with Inconel, but its basically a super high temp and super high chemical resistance type of stainless steel that I use to make headers/tubro manifolds. Its also a PITA to weld, but easy to tool. If stainless steel is out of the question, would Inconel be a safe option?

Thanks in advance,

-Luke
 
I'm no metallurgist by far but we use 316L SS for our control systems that basically live out in the gulf after time it will get some surface rust but doesn't corrode. We also use inconel on certain parts of blowout preventers, this is some tuff stuff but very impractical IMO for a fish tank lol titanium holds up better than 316L ss in salt water IMO.
 
There is a fairly high grade of SS that is suitable for saltwater, I have no idea what the actual grade is but it is out there. I am sure for testing purposes you can get away with any SS, just check it regularly for corrosion.
 
316 is what I was trying to come up with, scooty and I were posting at the same time.
 
Actually, Hastalloy, Inconel, and Titanium are about the best for saltwater use. The problem with stainless is the nickel interaction with the chlorides, I'm sure you've heard of chloride stress corrosion? In high temp applications it's a real problem, not much of one at out tank temps though. Even using SS 316/L I've had bolts rust away with in 6 months being immersed in salt water. If I was prototyping something I would use one of the 6000 series aluminum or 303 stainless. It's cheaper and would be fine for limited use, i.e. 6 months or less.
 
I think we all agree on that but at what cost, is it worth it for a fish tank, now that I read back he wants something that would be submersed in sw, so I agree ss will eventually cause problems, probably why titanium is more commonly used for sw equipment.
 
After making the above post I have been asked some very good questions via PM’s. So here is my response. Chloride stress corrosion can best be described as the fracturing of the metal when exposed to chlorides. This condition is typically found in high temperature environments, i.e. the process cooling water pipes for nuclear reactors and other processes. The chlorides can be in the form of salts or even PCP containing oils. Another good example is swimming pools that use chlorine for water treatment. I found some useful information on the web that answers many questions.

http://www.corrosion-doctors.org/Forms/scc.htm
Here are some pertinent excerpts from the above site;

Stress Corrosion Cracking (SCC) Defined
Chloride SCC
One of the most important forms of stress corrosion that concerns the nuclear industry is chloride stress corrosion. Chloride stress corrosion is a type of intergranular corrosion and occurs in austenitic stainless steel under tensile stress in the presence of oxygen, chloride ions, and high temperature. It is thought to start with chromium carbide deposits along grain boundaries that leave the metal open to corrosion. This form of corrosion is controlled by maintaining low chloride ion and oxygen content in the environment and use of low carbon steels.
Preventing or controlling SCC
The most effective means of preventing SCC are: 1) properly with the right materials; 2) reduce stresses; 3) remove critical environmental species such as hydroxides, chlorides, and oxygen; 4) and avoid stagnant areas and crevices in heat exchangers where chloride and hydroxide might become concentrated. Low alloy steels are less susceptible than high alloy steels, but they are subject to SCC in water containing chloride ions.

You may want to visit the site for some good pics on what can happen when these condition are met.
I would like to say that using stainless in the aquarium environment is substantially less stressful than in a nuclear plant or even is waste processing, but I know from my own experience that stainless will not last being immersed in saltwater.
I hope this clears up any questions anyone has.
 
hey luke, glad to hear your moving on your project. i dont know how hard it would be to get but what about ceramic? and i would be interested in that aragrosrete bbq. mentioned elsewhere.
 
jsmkmavity- Thanks, it was tough to convince my boss that I wasnt the ONLY person in the world that cared about growing corals. I showed him reef-central, and he was like, ok ok, I belive you, there is a buyer group.

I would try out ceramics, and maybe as a final version material, but I just dont have any skills with it. I dont have a kiln either, nor would I know how to use it for cureing structural type ceramics even if i had one. Metal is kinda my forte for building things that need to be frequently changed around.

Les- I have lots of 6xxx series aluminum, and 7xxx series as well. Even some special alloys from boeing areospace that are stamped "T8" with no additional numbers... I'm pretty sure all those alloys have copper them though, and I've heard that aluminum itself is a trouble maker in aquariums, so I would be a little hesitant to use it unless I could chemically anodize it with a nice coating of aluminum oxide before sticking it in the tanks.

Thanks for the advise, I will just assume that the chloride SCC wont be able to occur at temps in the 80F range. It sounded like a process that needs to get materials excited a bit for it to work.

I'm really hopeing that Boomer will chime in here and shed a little light on what would be an ideal metal for me to dork around with.
 
Steel becomes brittle when exposed to chlorine and chlorides. I believe this is due to the chlorine radicalizing and extracting the Nickel from the metal. So I would be concerned about nickel posioning the fish/corals. Nickel, especially as Nickel Chloride, is extremely aggravating to living things. Some people, and I am assuming animals, are hyper allergic to nickel. I have a friend who will break out in a rash just from NiCl fumes.
I would likely implement an aggresive water change while testing the stainless steel components just to make sure the leached components don't build up to fatal doses.
-chris
 
For prototype work, I would go with 316L stainless rather than any of the aluminum alloys. Aluminum alloys just don't do well in saltwater.

By the way - the 7xxx aluminums are higher strength alloys. The 7xxx is not considered weldable but I believe the 6xxx series is. The T8 designation is just the type of heat-treatment that was used on that particular piece of aluminum. It is not an alloy designation. And it is the 2xxx series that has a lot of copper
 
Luke

nice coating of aluminum oxide = Phosguard, X-Phosphate, Phosphate Sponge, etc.

So coat it with phosphate remover :) Not sure that is a good idea ;)

Aluminum and aluminum-based phosphate binders
http://www.advancedaquarist.com/issues/july2003/chem.htm

Many use 316, as posted. I use to know a guy, a metallurgist, where is daugthers salt water store had all tank frames made of 316, by him. I never say an issue in 2 years, but those are frames

Steel and steel typies is a whole field by itself. I'm sure you know that. What are these parts you are talking about. I have run many filters and powerheads for years with SS pins and it is not an issue.

Got money, I like to spend peoples money :lol:
http://www.woodheadpublishing.com/en/book.aspx?bookID=1077

http://www.knovel.com/knovel2/Toc.jsp?BookID=780

You need to read these
http://www.hghouston.com/ss_comp.html

http://www.aquadevice.com/english/05material_y130n.htm

http://www.azom.com/materials.asp LOTS HERE

http://www.azom.com/details.asp?articleID=1177

http://www.msm.cam.ac.uk/phase-trans/2005/Stainless_steels/stainless.html

http://www2.sandvik.com/sandvik/014...InternetWeb)/1BF822261FC38B3CC1256DE10047716A

Have you looked at Monel or Yokota YST130N. Many seawater aqauium facilities are using or going to YST.

http://www.aquadevice.com/english/05material_y130n.htm

Did any of this shit help ??
 
Thanks Boomer, I have a very small budget, but buying books is something I always can make a few sacrifices to get my hands on. I will first dig through the local college resources for those books before I try to buy them though ;) its good to be a student :D


Looks like that yokota material would be an effective Ti alternative, possibily even better. Unfortunately I'm not aware of any local and free/cheap sourceing for it, and if I end up spending over $100 on R&D I'm going to be VERY dissapointed as missing my development project goal.

I will do some looking around, and thank you very much for the info.

Can you think of any danger to the corals that might occur with just something like 316SS? Because if its simply a matter of the prototypes corodeing away, I couldnt care less. I just dont want the byproducts of the corosion to be dangerous to the corals.
 
I have zero educational experinece on this subject. I have a welding textbook, and Engineer to win By Carrol Smith, worn this book to shreads. Just enough to sorta understand what is what, and sorta why it is what it is. LOL
I do want to share this, I am sure you already know it, but just as a reminder in case.
I was on the Albany, I was a sonarman. We pumped the sonar dome out to do a routine inspection of the 1144 hydrophones in the sperical array. It was kinda interesting. Newport News had used one type of stainless steel for the studs (4 each) and one kind of stainless for the selflocking nuts. The result was galvanic corrosion. The hydrophones were loose, and able to move around. The studs were corroded, and the nuts were just about ribbons. It was a bad situation. So basicly what I am saying whatever you pick stick with it. All the stainless pins in my pumps are fine. I cant see where it could cause a problem for R and D. As long as its not the "it looks like stainless lets call it stainless" stainless steel.
 
wrightme43 said:
I have zero educational experinece on this subject. I have a welding textbook, and Engineer to win By Carrol Smith, worn this book to shreads. Just enough to sorta understand what is what, and sorta why it is what it is. LOL
I do want to share this, I am sure you already know it, but just as a reminder in case.
I was on the Albany, I was a sonarman. We pumped the sonar dome out to do a routine inspection of the 1144 hydrophones in the sperical array. It was kinda interesting. Newport News had used one type of stainless steel for the studs (4 each) and one kind of stainless for the selflocking nuts. The result was galvanic corrosion. The hydrophones were loose, and able to move around. The studs were corroded, and the nuts were just about ribbons. It was a bad situation. So basicly what I am saying whatever you pick stick with it. All the stainless pins in my pumps are fine. I cant see where it could cause a problem for R and D. As long as its not the "it looks like stainless lets call it stainless" stainless steel.
Click to expand...
And just for refference this happened in less than two years of operation.
 
Galvanic corrosion relies on stray voltage wandering around though IIRC. I admit there's probably some in most of our tanks, but it should be minimal compared to what is dealt with on boats.

I suppose you could drop a zinc into your sump and call it good. :p

-Dylan
 
Luke

You forgot :) What parts are we talking about ? A pin here or there to the whole flippin' thing is SS ? How is this, many have asked about SS on the chem forum and Randy always gives 316 for example, if DIY say a grounding probe.

Me on a 316 question;

Bryan
No, not a good idea for chiller tubing. The tubing is to thin and is more subject to corrosion and pitting. 316 really doesn't like chlorides, which are at 19,000 ppm in seawater. The problem gets even more serious if the tubes get dry which just accelerates the problem. So, there will be leaching of metals into the tank. Those bad leachables will be nickel and chromium. The 316, along with that thin tube, will cause stress fractures in the tubing from the chlorides, which will cause "Freon" to leak out. Go with the Ti, it will last for many years

316SS

Fe = <0.03%
C = 16-18.5%
Cr =10-14%
Ni = 2-3%
Mo = <2%
Mn = <1%
Si = <0.045%
P = <0.03% S

Randy
FWIW, I use 316 SS as part of my float switches. I think it is fine for an application like that. I do not know how well it would hold up for chiller tubing, where a pinhole could be a big problem.

Me
Not in my mind it is't Gary. I would rather see a better grade than 316SS. And no way for a chiller tube. The new silica coated 316SS maybe something different, haven't seen it in our application

I then posted this PDF

http://www.stainless-steel-world.net/pdf/11003.pdf

On another thread

As Randy has said it should be fine. Here is a link to the dif in comp of 316 SS and 316L SS

Corrosion Resistance
Type 316 is more resistant to atmospheric and general corrosive conditions than any of the other standard stainless steels. They have good resistance to the corrosive effects of sulfates, phosphates, and other salts as well as reducing acids such as sulfuric, sulfurous, and phosphoric. These grades are less susceptible to pitting on applications where acetic acid vapors or solutions of chlorides, bromides, or iodides are encountered. If heated to the range of 800° - 1500° F or cooled slowly through this range, the low-carbon version (316L) should be selected to avoid intergranular corrosion.

I gave this link for 316

http://www.azom.com/details.asp?ArticleID=863
 
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Mag Drive pumps have several SS screws holding there pump covers on. I lived on a boat for 8 yrs and 316 well work fine but if you have to weld it the weld joint well not hold up nearly as well.
 
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