18/10 vs. 18/8 and 18/0 stainless steel for flatware and pots & pans

A. Previously on another Internet forum:

Question
I would like to know about stainless steel, specifically which is stronger and will last longer 18/10 or 18/8. which would make a heavier weight flatware ? I can't find these answers anywhere. Thank you so much.

Answer
Hello Shelly! Let me start with a few basics, OK? The 18/8 and 18/10 designations are older terms, and refer to the amount of chromium and nickel alloyed with the iron, to comprise the stainless steel. The 18/8 name has been pretty much replaced, in the States at least, by several other designations. 301 stainless steel has 16-18% Cr, and 6-8% Ni 302 stainless steel has 17-19% Cr, and 8-10% Ni 304 stainless steel has 18-20% Cr, and 8-10.5% Ni. That may explain your difficulty in finding information on these alloys. Similarly, 18/10 is usually referred to as 316 stainless steel, with 16-18% Cr, 10-14% Ni, and also 2-3% molybdenum, which greatly increases the resistance to pitting corrosion in seawater. Good stuff, that moly.

Now the mechanical properties these 300 series stainless steels are all the same! In the annealed condition, they are all listed at 75 ksi tensile strength, 30 ksi yield strength. The slight difference in Cr and Ni isn't enough to cause a difference in the strength by themselves. These alloys can be made harder, however, by cold working, i.e. rolling or drawing through a die or extruding through a die or some other such process which will deform the metal, while it is at most a few hundred degrees F. Here, too, the mechanical properties are the same: half-hard stock, for example, has 150 ksi tensile, 110 ksi yield strength, no matter if it is 301, 302, 304, 316, etc.

The difference is in the corrosion resistance (which I assume you're not interested in, since all will be fine for flatware) and in the ductility. A lower alloyed 301 has more ductility when work hardened than the higher alloyed 316. So after you stamp out your quarter hard sheet into forks, you can bend one of the tines more often, or farther, if it is of 301 rather than if it is made of 304 or 316, before it will crack. The weight of the flatware will depend on geometry, since the densities of the stainless steel grades are identical, for practical purposes. Iron, chromium, and nickel all weigh about the same. A splendid source of information on stainless steels is the Nickel Development Institute, at www.nidi.org, which offers a lot of FREE literature they are glad to send. And please don't hesitate to ask here again! (Gosh, I hope I answered your question in all this rambling!) Take care!

A. Hi, Amanda.

• 18/0 would mean 18 percent chromium and 0 percent nickel
• 18/8 indicates 18 percent chromium & 8 percent nickel
• 18/10 indicates 18 percent chromium & 10 percent nickel.

Because nickel costs about $17 per pound, much more than steel or chromium, flatware which contains none would be less expensive than flatware which contains 8 or 10 percent nickel.

While 18/0 is not necessarily unsatisfactory (and some people who are concerned about nickel even feel it is better), it is more prone to rusting as it is not as corrosion resistant.

A. Gabriel,
The demo you saw was no doubt carefully configured to show the seller's cookware in the best light. Still, 316L is more corrosion resistant, although probably no "safer", than the other stainless steels mentioned on this page.

Elena,
Although I doubt the "pores" theory per se, it is true that some stainless steel is electropolished rather than mechanically polished. When something is mechanically polished, under magnification it looks like a plowed field, whereas when electropolished the burrs are dissolved away, resulting in looking under magnification like ocean swells. 316L is a very good grade of stainless steel. It means type 316 (sometimes called 18/10) "L"ow carbon.

A. I have found a number of third-party sources that verify the superiority of 316 steel, versus lower grades of stainless steel on the market such as 304 and 18/8.

Here is some very interesting data on 316 steel, according to the Sandmeyer Steel Company:
http://www.sandmeyersteel.com/316-316L.html

Here is a quote from this page:

316 steel is used in the "manufacture and handling of certain food and pharmaceutical products where the molybdenum-containing stainless steels are often required in order to minimize metallic contamination."


Here is a website where I found that Pharmaceutical companies use 316 steel for purposes of high purity in their products:
http://www.arcmachines.com/appPages/weldspec02.html
Ed. note Dec 2013: that link is now broken

Here is a quote from this page:

"The Baseline series of PHARMACEUTICAL ENGINEERING GUIDES was developed by ISPE in cooperation with the FDA to establish a baseline approach to new and renovated facility design, construction commissioning and qualification. . . . discusses material selection for piping systems and recommends type 316L as the preferred steel for a High Purity Water generation and distribution system. "

I also have data from multiple Allegheny Ludlum metallurgical studies that demonstrates the differences between 304 steel and 316 steel.

Hi Joseph. Thanks. Yes, 316 is more corrosion resistant than 304, and yes, in limited circumstances (when welded) 316L is more corrosion resistant than type 316 (because during welding at white hot temperatures the carbon tends to migrate causing corrosion-prone accumulations and the lower carbon content of 316L minimizes that issue). But out-of-context quotes might add more confusion than clarification :-)

For example, minimizing metallic contamination may be of significance for electronics manufactured in a cleanroom if strong acids are used which can dissolve stainless steel; much less so with food, which is not a strong acid. And the fact that 316L is used in manufacturing has to do with the fact that the machinery is welded, and 316L is a tiny variation of 316 tailored specifically for welding; cookware is not welded. And when they speak of "High Purity Water", they don't mean "clean" water, they mean mixed-bed de-ionized water, an aggressive fluid used in semi-conductor manufacturing which is too pure to safely drink. Thanks again.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 20, 2012

A. OK, back to the original question -- what grade of stainless steel should I use for cooking utensils?

I work for a company that fabricates carbon steel and stainless steel piping systems for food processing plants, water treatment plants and industrial users. My job is to help with selecting the best (most cost-effective) materials for our customer's specific applications.

18-8 stainless steel -- now most often referred to as 304 or UNS S30400. -- Good, general purpose stainless steel. Used for some drinking water plants, petrochemical plants, lots of structural uses. If you want to make transit bus handrails, use 304. It's resistant to most chemicals, and won't pit or corrode from people's sweaty hands. Good for cooking utensils, but not as goods as 316.

18-10 stainless steel - now most often referred to as 302 or UNS S30200. About the same for food use as 18-8. Lots of good, inexpensive cookware is made with this alloy.

18-10MO - now most often referred to as 316 or UNS S31600. This is the alloy of choice for food processing equipment and applications requiring excellent corrosion resistance to most chemicals. 316 has 18% chrome, 10% nickel and 3% molybdenum. The molybdenum has a major effect on resisting acidic and chloride corrosion. Lots of foods are acidic -- tomato sauce is one that will pit 304 but not 316. Just about everything you cook has salt in it, and salt (especially sea salt) has high chloride levels.

However, most if this is irrelevant. Unless you're running a meat packing plant next to the ocean (and they all use 316), any of these grades of stainless will work just fine.

How to destroy stainless steel cookware:

> Use with plain steel items. In our plant, we carefully segregate stainless steel from plain carbon steel. All of our shelves are coated with plastic so the stainless steel never touches carbon steel. Having both types of steel in contact may cause the stainless steel to develop surface rust. Using stainless steel spatulas on cast iron frypans may cause rust marks to develop on the spatula. Don't use plain steel wool to clean your stainless steel pots -- use a Scotch-Brite pad ⇦this on eBay or Amazon [affil links] or stainless steel wool [affil links].

> Let them soak for hours. Leaving your spaghetti sauce pot in the sink full of tomato-y water is the perfect way to start pitting. Stagnant acidic water is the worst thing you can do. When we design tanks for food processing plants, we take special care to make sure the tanks can completely drain and there are no crevices to collect stagnant water.

Bottom line, any good-quality 18-8, 18-10, 302, 304 or 316 stainless cooking utensils will be head and shoulders beyond most of the other available materials. Teflon-coated pots chip and flake, glass breaks and discolours, copper tarnishes and often contains lead, strong detergents dissolve aluminum.

As for the demo, it's a trick. When the nice SaladMaster salespeople boil water in your pots and pans, you're comparing the results against the brand new, never-been-used SaladMaster pots they brought with and unwrapped in front of you. Your pots and pans have millions of microscopic surface cracks that may trap equally microscopic food particles. That's what you taste -- the boiling water and baking soda leaches out some of the food particles, causing the yucky taste. The brand new SaladMaster pots have never been used, so no food in THEIR microscopic cracks, so no taste.

A. Hi, Gail. Please try to read the replies slowly and ask for clarification on any specific points you didn't understand. Repeating what has been asked and answered doesn't eliminate the confusion -- it just makes it progressively worse for each subsequent reader :-)   

All stainless is about the same density and unit strength, but thicker flatware is heavier and stiffer. More nickel is more corrosion resistant, and more expensive. 316 (sometimes called 18/10) stainless steel is best, and 304 (sometimes called 18/8) is almost as good. But I don't think you can really select flatware on this basis, because there is more to the process of manufacturing good stainless steel than just the alloy composition. I think you can go only by the reputation of the maker and their guarantees.

Although I am a proponent of "Buy American", I believe that no stainless flatware is made in the USA^^{See entry of July 19, 2012 for update}. It's almost all made in China today, and I have zero confidence in the American companies selling it. If anybody knows of American-made place service, please pipe in.

I have little experience with Japanese flatware but, unlike so many American companies today, Japanese companies don't seem to engage in "meatball whoring" (the deceitful practice of selling their meatball logo to any schlock outfit to slap on their low quality product in exchange for licensing fees) -- so if it's got a Japanese name, I'd be more likely to trust it wherever it's made.

Based on what I can see, their lifetime guarantee, and customer reviews, my guess is that Yamakazi is one of the better flatwares today. If anyone has personal experience with it, please chime in; meanwhile we've linked to reviews on Amazon where the customers rated it "5-star".

Good luck.

P.S. -- Update Sept. 2012: We bought French-made Guy Degrenne stainless flatware from Williams-Sonoma last Christmas, and are happy with it.

A. I just bought a set of Yamazaki and all I can say is that I think it is very important to have flatware that feels good in the hand, has a good weight and looks beautiful...and this brand delivers on all counts. It is marked 18/8 and "made in China", and while I don't know how it will wear, my initial impression is that it is well designed, well made, and that the company pays attention to quality. No small thing these days!

A. If you read between the lines, the key factor in the ratings is the amount of Nickel in the item. The Nickel is the metal that reduces the rust and pitting of the base metal, being Stainless Steel. Stainless Steel is a combined metal of steel, nickel, chromium, titanium and others. The SS rating also indicates a hardness, as 21 will be harder and stronger than 14, though less flexible, meaning it should last longer in use. The second number in the equation for flatware as in 18/10, being the 10, indicates the percentage of nickel being used. Most common ratings as in 18/8 - 18/10 are the basic and accepted range for flatware. A 21/0 therefore is a strong SS with minimal nickel content. Most of these utensils have been polished. With minimum nickel content, the polish will not hold up very long and will lend itself to staining long term.