I think we discussed stainless steel pins before with me on General Questions, but I have a new question. I did not do a search to add this part on. I hope that is OK.
If I try to rust a stainless steel pin, to see how much nickel or other things are in it should the container be airtight or have air available?:rolleyes:
Technicalities aside, iron cannot “rust” without oxygen, so yes, you need the presence of air.
Thank you very much. Yes, I forgot the iron, which is what actually rusts. When we discussed it earlier, it was said there are different qualities of stainless steel and there can be nickle, iron, etc. The worse the stainless, the easier it is to pick up with a magnet. Which I can with these. But the lack of rust is what I care about. I will add air. Thanks again.
Are you sure about this? I know there are different stainless grades, and some are “magnetic” (in the sense that a magnet will pick them up). I just thought that the different formulas were for different applications that required different physical properties. Or does “worse” here just mean in your application?
I think you are confusing austenitic stainless steel with ferritic and martensitic and others. Austenitic stainless steel is not magnetic, and it is by no means poor quality. In fact, some rather useful and valuable items are made from austenitic stainless, such as a lot of food preparation equipment, oxygen and CO2 cylinders, and some laboratory equipment. In fact, when I think of “corrosion resisitance” I typically think of austenitic (non-magnetic) stainless steel.
Thanks Anthracite. I was aware (vaguely) of the other types, although the technical names escaped me. I think my problem was that in the post I replied to I read “worse” as “of poorer quality”, when “less corrosion resistant” may have been all that was meant.
Are you actually trying to do this?
Lots of different grades of SS
Just processing SS can alter the alloy - so rusting will change the equation. The magnetic properties do not denote the qualities. There are different alloys for different uses.
Don’t know why this did not occur to me.
If this is an experiment, thinking about the OP, you would have to have something to act on the other metals - need O to rust Fe.
Using electrolysis is a much faster way of seeing it’s content. I use electrolysis to clean encrusted coins, and I usually use a stainless steel pin as the item connected to the positive end of the battery. Usually after two hours the pin would be in pieces, allowing me to see the insides easily.
Can you explain what you mean by “processing” in this sentence? Because, and I could be mistaken, I do not think it is correct as written.
Welding, grinding, heating, certain types of cutting, even running a tube through a bending machine can cause enough steel to be scraped into the surface of the metal to cause problems.
Welding, grinding, heating, certain types of cutting, even running a tube through a bending machine can cause enough steel to be scraped into the surface of the metal to cause problems.
For medical grade ss tubing, as used in catheters and stents, it is neccessary to ‘passivate’ after any process that exposes new surfaces, eg grinding. We’re talking top quality tubing here. Passivation scavenges free Fe from the surface and leaves a chromium risk layer to prevent corrosion. Without this- rust.
(I am not a metallurgist so feel free to nitpick)
chromium rich layer of course
Different stainless alloys have different mechanical properties, but if you are concerned first and foremost with corrosion resistance, the best common alloy to use is ASTM type 316 stainless. This stuff is commonly used for parts exposed to harsh environments, like immersion in seawater, for example. 316 is not commonly used for tools and knives, since it does not hold an edge as well as the martensitic grades, but they do make diver’s knives with it, and a few special purpose items where corrosion resistance is the more important factor.
316/316L is good stuff but if the application involves steam then 2275 is the ticket. Still got to passivate it.
I don’t think you understand what I’m saying. An alloy is a mixture of metals and non-metallic compounds that is typically consistent throughout its makeup. Grinding, heating, cutting, and extruding a tube is not going to change 316 alloy to something other than 316. Note I purposefully left out “welding”, as the weld region can, unless same-metal MIG or TIG welding is used, create a whole new alloy. And I understand quite a bit about changing a surface oxide or chromium-rich layer, but that does not change the alloy of the piece. Please see the AISI handbooks for further information.
I’m curious what you base your comment regarding 316 on? What is your experience in working with it? According to Combustion Fossil Power, 4th Edition, 1991, Chapter 17 pg. 17-3 through 17-5, 316 is in fact used for steam applications. I quote:
See also Table I - “Materials Used in Boiler Construction”, where the types listed are:
and other austenitic stainless alloys are listed as well, such as TP304H, 304, 304H, TP321H, etc. Oddly, the type 2275 you mention is not listed in that reference nor in the fairly authoritative Babcock and Wilcox Steam book (40th Edition, Chapter 6) as being suitable for steam boiler tubing. Perhaps only for low-temperature and low-pressure applications…?
My comment is based on several parts for a steam generator that I was fabricating. In the prototypes, parts made with 316 would fail - the 2275 is what we used for the production of the final unit.
I was also thinking about the OP. There was a post about rust. If the pin had been used or stored with other parts, it is possible that some extra rust could be impregnated in the surface of the pin.
This is very interesting. I think I started a stainless pin topic and also the rust topic. I am presently trying to rust 2 stainless steel pins. They have been in a wet paper towel, now for about 2 weeks and nothing has happened. I will carry on and endure with my experiment. . . . or is it time to stop?