302 vs 304 stainless steel in cookware
Q. I was recently in the home of a friend for a cooking demonstration. In the demonstration, I was told that 304 is superior to 302 stainless steel for cooking basically because it was not reactive with food products and therefore would not leach into the food etc etc. The salesman attempted to prove this by dissolving sodium bicarbonate..... which he called "pure sodium" into boiling water placed in various types of pans.... 302, aluminum, glass etc, and then having the audience taste the difference in the water to prove that 304 did not react but all of the others did.
The salesman also went to great lengths to convince us that it was possible for the aluminum, (used in cookware to more evenly distribute heat) to leach through 302 stainless and get into the food.
Is any of this true or am I correct in my assumption that the salesman was .... "misguided"John Barile
consumer - Raleigh, North Carolina
A. He is correct in saying that 304 is better than 302, but only slightly. 18-8 is even better but not used that much. He is absolutely wrong about the aluminum leaching thru in any detectable quantity thru the 302 or 304.
Snake oil salesman. Buy from him at your own risk. I would not, but that is me.James Watts
- Navarre, Florida
Q. I read in a "stainless steel" website that 304 contains 18% chromium and 8% nickel, thus it is commonly referred to as 18/8. However, James Watts of FL seems to be saying that 18-8 is better than 304, which means 304 and 18-8 are different? Can somebody clarify? In Malaysia, the stainless steel that we commonly see on cookware are only 18/8 and 18/10. Most of it comes from Thailand (Zebra Brand). My question is, which is better, 18/8 or 18/10?
Thank you.Phillip Ooi
- Petaling Jaya, Malaysia
A. 18-8 refers to a class of stainless steels including 302, 304, 316, 347 that have a chromium content of approximately 18% chromium and 8% nickel. They all have approximately the same corrosion resistance however the different alloys have different characteristics that make them easier to machine or offer more corrosion protection under different environmental conditions. 302 and 304 are frequently used interchangeably. The main difference is 302 has .08% carbon versus .15% for 304. Additionally 304 generally contains 1-2% more chromium than 302. I would guess any differences in cookware would be minimal.Dale Neff
- Glendale, California
March 12, 2008
A. Dale Neff and Phillip Ooi almost got it right.
Both 302 and 304 are known as "18-8" stainless steels, as are several other of the 300-series stainless steels (300-series stainless steels are called "austenitic" stainless steels), the 18-8 referring to the "average" amount of chromium and nickel in their chemistries, and the min/max levels vary only slightly for the 302 (17-19 Cr) vs. 304 (18-20 Cr). .
However, 302-stainless is the alloy with the higher carbon content, not 304, and it should be noted, too, that these carbon contents are maximums only. Thus, 302-stainless has a maximum of 0.15 percent carbon, and 304-stainless has a max of 0.08 percent carbon (both alloys usually have less than their maximums). Because 304 stainless is able to control the carbon levels better, it is the most frequently used stainless alloy today, rather than 302.
Both of these stainlesses will perform very well in cookware, and one is not to be preferred over another from a metallurgical point of view as far as performance is concerned.
John Barile points up a common mistake many people make, namely that of believing everything they are taught. Obviously the salesman was saying what he was taught, and is a clear example of the blind leading the blind.
Take comfort in knowing that any stainless cookware you have at home is safe, does not allow food to leach through it, is highly corrosion-resistant, and should give you a lifetime of good service if not abused.
metallurgical brazing consultants - Simsbury, Connecticut
September 10, 2009
Q. My friends and I are considering doing a group buy of T316 stainless steel mesh (10 strand) to use in food dehydrators. I've been told (by someone at the manufacturing company) that the chromium and nickel levels are higher in the T304 and that the T316 would be safer for this application. Does anyone have any information about that?Julie Mallalieu
hobbyist - Eugene, Oregon
September 10, 2009
A. Hi, Julie. No, the reasoning is not correct, as you can see from the previous postings on the page. However, T316 is more corrosion resistant than T304 and the manufacturer may have been trying to make that point. Good luck.
Ted Mooney, P.E. RET
Pine Beach, New Jersey
December 3, 2009
Q. T316 is more corrosion resistant than T304, then it should be better for cooking as salt over time would corrode T304 and other stainless steel cookware. If that happens where is that metal going? I would think in our food and in our bodies like all the other cookware out there. Is this correct?John Broussard
Construction - Lafayette, Louisiana
July 26, 2012
Q. I am looking to manufacture 1/4" 20 bolt/nut hardware for outdoor usage (non-marine) and have the choice of using 302 or 304 stainless steel. I've seen conflicting information on the difference in corrosion resistance of these two grades.
The manufacturer is quoting double the cost of using 304 over 302.
Strength is not so much a factor as the bolt /nut combination does not have much of a weight load.
I have been buying 18/8 304 grade for other projects as this is readily available.
Looking for facts or experience of using 302 versus 304 material to manufacture bolts/nuts.
- Park Ridge, Illinois, USA
A. There is no difference in resistance to general atmospheric corrosion between Type 302 (UNS S30200) and Type 304 (UNS S30400). For fasteners that are cold formed (cold headed), there is a modified grade such as Custom Flo 302HQ from Cartech that includes 3-4% Cu for reduced work hardening & improved formability. The official designation is UNS S30430, and it has similar corrosion resistance to the other two grades. There is no substantial difference in the cost between 302 and 304 relative to alloying content, so any differences being quoted must be due to different manufacturing processes, suppliers, availability, etc.Toby Padfield
Automotive supplier - Michigan, USA