0

This ball valve is stamped with 304.

304 is supposed to be stainless steel.

Does 304 mean stainless steel? will it rust?

It isn't used yet, how come there is already rust inside?

If i use it, will i expect more rusts?

enter image description here

enter image description here

6
  • which part is stainless steel? .... why do you assume that 304 means stainless steel? ... it could easily be a manufacturer part number
    – jsotola
    Nov 1, 2020 at 3:36
  • the seller said 304 means stainless steel.. but if it's really 304.. does 304 ever rust?
    – Jtl
    Nov 1, 2020 at 3:41
  • the ball is probably stainless steel and maybe the retainer also .... the valve body material is uncertain
    – jsotola
    Nov 1, 2020 at 4:18
  • 1
    That is likely just a bit of dirt. I would be more concerned about the reduced diameter - this is obviously a cheap one as the ones I used to purchase had a larger diameter valve section.
    – Solar Mike
    Nov 1, 2020 at 5:46
  • 1
    Stainless steel means it stains less, otherwise it would be called stainfree steel. In all seriousness, all steels can rust if not taken care of, it's just more resistant than ordinary steels. Nov 1, 2020 at 6:08

3 Answers 3

4

304 will rust, to an extent. It's not shocking or surprising. Plenty of examples if you do an image search - in my case, personal experience.

However, my best guess on that very isolated spot is that it may have had a speck of regular carbon steel from the manufacturing process, which rusted there.

2
  • Is stainless steel made from carbon steel? If its really a speck of carbon steel. How do you fix the rusty spot?
    – Jtl
    Nov 1, 2020 at 20:43
  • 1
    Tooling is used to cut items being manufactured. If it bothers you, polish it clean. It's truly nothing to be concerned about.
    – Ecnerwal
    Nov 1, 2020 at 22:19
3

This ball valve is stamped with 304.

Hey if you want me to take a dump in a box and mark it guaranteed, I will I got spare time. But for now, for your customer's sake, for your daughter's sake, ya might wanna think about buying a quality product.

304 is supposed to be stainless steel.

supposed to be.

Does 304 mean stainless steel

stainless is supposed to mean a minimum of 10.5% of chromium alloyed with steel, and i'm not sure if that's even a formal definition or just an industry accepted value. 304 per definition by ASTM or whoever you consider the authority is supposed to have 18% chromium, and some nickel content. Better grades such as 316 will have other alloying elements such as molybdenum, in addition to more percentage of chromium and nickel. You can look up definition of stainless grades online easy enough, example: https://www.fenestration.net/pdf_documents/Stainless-Steel-Types.PDF

304 is the most common and least expensive grade of stainless, and also the most counterfeit (put just enough chrome in to give a visual look of stainless and sell it on amazon or ebay).

will it rust?

yours in that pic, most likely. But even true SAE 304 stainless will rust in certain environments which is why there are many other grades or classifications of stainless steels, defined by the % of their alloying elements, such as 316 which is the second most common stainless.

It isn't used yet, how come there is already rust inside?

because it is a low quality product from china with a fraudulent 304 marking on it. The absence of any legitimate markings such as manufacturer and ASTM, SAE, ANSI or ISO should be the first clue.

If i use it, should i expect more rust?

don't be surprised. It depends on what you use it for, I'm sure it does some have chromium and nickel content so it will "stain" "less" than common steel. You do not have an stainless piece that meets ASTM 304 definition what you really have is a china made valve with a 304 stamped on it and just enough chromium for it to pass a visual and make the seller/manufacturer maximum profit since alloying steel with chrome and nickel costs money.

1
  • ASTM does not specifically list alloy compositions . Each individual ASTM specification will have it's own alloy compositions and tolerances . So ASTM specs for plate, sheet, pipe , etc. may have small variations in composition. SS 301, 302, 303, CF8 ( castings) are similar to 304. Some ASTM specs list 5 Cr as stainless but industry likely considers 9 Cr : 1 Mo as the leanest SS. Nov 2, 2020 at 19:33
2

Very likely the valve is 304 SS. The speck of rust is insignificant ,forget it , not worth thinking about. Possibly it occurred as some "rust" on SS equipment in industry; it may have been blasted with steel grit and one bit of grit imbedded in the surface. I have had to go over this story with a few managers. If you put 304 or 316 in seawater splash zone , they resemble carbon steel = rust badly.

4
  • Why does salt cause 304 or stainless steel to rust?
    – Jtl
    Nov 1, 2020 at 22:06
  • 2
    The subject of many PhD theses , papers , and books. And that does not count stress corrosion cracking , caustic cracking ,and my fav- polythionic cracking ; which can occur in an hour. And a few odd balls like liquid metal ; Amoco had to replace all the 316 piping in a chemical plant because of cracking caused by zinc. Nov 2, 2020 at 0:47
  • Say, can a chromium plated brass ball valve rust? i also have another one like this pegleryorkshire.co.uk/EN/Brands/Pegler/Ball_Valves/…
    – Jtl
    Nov 2, 2020 at 20:45
  • A corrosion pit on a brass valve that is chrome or nickel plated will have blue/green. corrosion product. Nov 3, 2020 at 21:13

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.