Does Propane Corrode Stainless Steel ?

[John Timmins]

I have reconditioned my 16 year old Ducane gas grill. I put new burners in it that are stainless steel.

Basically the burners are bent stainless steel tubing that has been crimped on one end and a bunch of holes let the gas through for the flames. I read that the burners have a limited life because the stainless is "corroded ?" by the propane?

Is this true ?

 

[copterdoctor]

I would think the hot/cold/hot/cold would be the reason for failure....

 

[NXGTS]

I have had a "Pefect Flame" grill for the last 6 years and have had to replace all 5 burners twice. I don't know if is the propane or just an extremely low grade stainless. I tend to think they are just making the burners as cheap as they possibly can.

 

[MoonRise]

Also keep in mind that stainless steel is stainLESS, not 'ThisSteelWillNeverCorrodeNoMatterWhat'.

Something I seem to have to remind my wife of regularly.

And also, the thin stainless steel sheetmetal burners are not only being exposed to the propane, but also the odorant in the propane as well as the thermal cycling and the food/grease dripping as well as dripping sauces/glazes/whatnot.

Thin metal doesn't have as much material there before even a bit of corrosion affects them.

Add in the thermal cycling and high burner temps and then all the 'crud' that can (or WILL) get on them, and gas grill burners don't have all that easy of a time.

http://www.gasgrillsnow.com/GasGrillFAQ.asp

especially

http://www.gasgrillsnow.com/hsburnthru.asp

http://www.gasgrillsnow.com/BurnerComparison.asp

 

[houdni]

depends what grade of stainless.... the marine grade stainless is stainLESS...i can give it cut it up ...leave it out in the hawaii weather and still have it shiny as if i just cut it that day...but that grade of stainless is very expensive...

 

[38Chevy454]

As a metallurgical engineer, here are some technical info points. There are many types of stainless steel, which is a name that is common, but it is really corrosion resistant steel. Being exposed to high temps as your burners are, and probably a lower grade stainless with less chromium (the alloy element that makes it "stainless"), you are getting high temp oxidation, which over time causes the metal to corrode. There is not much you can do except replace the burners when they get too oxidized (corroded).

 

[lilredex]

Would a magnet test weed out the lower gradesof SS?

 

[38Chevy454]

Would a magnet test weed out the lower gradesof SS?

In general, yes. For stainless steels, there are basically 4 types commercially avalailable.
1) 300 series, also called austenitic stainless. Most common you will find or run into. These are the best for corrosion. The common numbers you might see are 304, 304L, 316, 308, 303, 302. These all have about 17-18% Cr and also have about 6-8% Ni. The Ni makes them non-magnetic. Common used for silverware and cooking or food prep. Cannot be heat treated to make stronger, but can be work hardened to bring strength up. Used mostly for superior corrosion resistance.
2) Martensitic stainless. These are 10-12% Cr and not much else for alloying. Commonly used for exhaust systems on factory systems, and other less harsh environments. These are magnetic and can also be heat treated to make stronger. Such as cutting blades. Typical numbers you might find are 410, 440.
3) Ferritic stainless. Second most common commercially available, they are also magnetic. More likely to find around marine or other wet environments where they don't want as much cost as the 300 series. Not as good corrosion resistance compared to 300 series, but better than 400 series. Typical numbers are 409 and 430
4) Precipitation Hardening (PH) stainless. These are used where high strength is needed. Magnetic also, but pretty good corrosion resistance. Since they require heat treatment and precipitation hardening for max strength you need to design around this. Most costly to buy and process. They have 15-18% Cr and 4-5% Ni as main alloy elements. Typical numbers are 17-4PH and 15-5PH.

 

[Terry454]

Just curoius. I often see fasteners of 8-18 SS. What is this stuff like? My experience is that it just never corrodes, but I don't live near salt water.

Terry

 

[MoonRise]

Just curoius. I often see fasteners of 8-18 SS. What is this stuff like? My experience is that it just never corrodes, but I don't live near salt water.

Terry

18-8 stainless alloy is pretty much the 'same' as 304 stainless alloy. Commonly used for stainless flatware, although some recent flatware I saw was 18-0 (no nickle, just chromium).

It is a pretty 'standard' stanless steel alloy, but not 'super' stainLESS.

And keep in mind what I wrote earlier, stainless steel is stainLESS steel. 304/18-8 can still rust or corrode.

 

[metal tech]

321 & 347 S/S is used in the hot exhaust sections of some jet engines. Either of these 2 grades of stainless would be a good choice for grill replacement tubing. MSC & MCMAster Carr sell short lengths if you're interested. The lower grades lack some of the alloying elements that these two have for use at elevated temps.

 

[dladcock]

I have reconditioned my 16 year old Ducane gas grill. I put new burners in it that are stainless steel.

Basically the burners are bent stainless steel tubing that has been crimped on one end and a bunch of holes let the gas through for the flames. I read that the burners have a limited life because the stainless is "corroded ?" by the propane?

Is this true ?

One of the corrosives that is generated on burners comes from grease or animal fats mixing with water. Like a car engine, heated moisture and oil creates an acid that attacks metals. Moisture is a by-product of cooking/heating mixing with the liquid fats and dripping directly on the burners. Humidity is also attracted to the grease after the grill cools.To a degree, the mess is an insulator, holding high heat next to the burner. All grill manufacturers recommend burning off the grill, on high after cooking. This will help extend burner life.The light gauge, low chrome/nickle alloy stainless resists to a point, but a higher grade would last longer than the types used for replacement, and would be more expensive for sure. Propane also produces moisture as a by-product during combustion. All considered, a grill burner has a tough life.

 

[darkk]

They make trac pipe (corrugated stainless steel)for propane so it can't corrode to quickly or it wouldn't pass building codes.

 

[Beaumont67]

I have a 15 year old natural gas grill.
While the sheet metal box pan is rotting out now, it still has the original S/S burner.

Once a year, I pull out the burners, drill each & every small hole to remove the carbon buildup / to ensure it produces a strong & even flame.
After drilling, I flush the burners with a garden hose...works-4-me.

------------------------------------------------
Beaumont { :>)) www.petperfectexpress.com
1965 Malibu S/S, 1966 Beaumont Custom original paint, 1967 Beaumont Custom, 1967 Beaumont Custom original paint, 1967 Beaumont 396-350HP Sport Deluxe M21-411's - SOLD 1970 Judge

 

[Norcal]

They make trac pipe (corrugated stainless steel)for propane so it can't corrode to quickly or it wouldn't pass building codes.

It's called CSST, & there have been issues w/ pin holes. The "fix" was to increase the bonding conductor size from 12 AWG to 6 AWG, gimme black iron pipe for gas anyday, but that is a whole different subject matter, that belongs in another thread.

 

[mrobins297aaa]

In general, yes. For stainless steels, there are basically 4 types commercially avalailable.
1) 300 series, also called austenitic stainless. Most common you will find or run into. These are the best for corrosion. The common numbers you might see are 304, 304L, 316, 308, 303, 302. These all have about 17-18% Cr and also have about 6-8% Ni. The Ni makes them non-magnetic. Common used for silverware and cooking or food prep. Cannot be heat treated to make stronger, but can be work hardened to bring strength up. Used mostly for superior corrosion resistance.
2) Martensitic stainless. These are 10-12% Cr and not much else for alloying. Commonly used for exhaust systems on factory systems, and other less harsh environments. These are magnetic and can also be heat treated to make stronger. Such as cutting blades. Typical numbers you might find are 410, 440.
3) Ferritic stainless. Second most common commercially available, they are also magnetic. More likely to find around marine or other wet environments where they don't want as much cost as the 300 series. Not as good corrosion resistance compared to 300 series, but better than 400 series. Typical numbers are 409 and 430
4) Precipitation Hardening (PH) stainless. These are used where high strength is needed. Magnetic also, but pretty good corrosion resistance. Since they require heat treatment and precipitation hardening for max strength you need to design around this. Most costly to buy and process. They have 15-18% Cr and 4-5% Ni as main alloy elements. Typical numbers are 17-4PH and 15-5PH.

very informative post

when we were doing HVAC for waste treatment plants almost all the ductwork was 316 or fiberglass below what they would call the water line or wet well. when the sewers would get a over flow condition a lot of that stuff ended up under sewage water for awhile.

 

[38Chevy454]

321 & 347 S/S is used in the hot exhaust sections of some jet engines. Either of these 2 grades of stainless would be a good choice for grill replacement tubing. MSC & MCMAster Carr sell short lengths if you're interested. The lower grades lack some of the alloying elements that these two have for use at elevated temps.

321 and 347 are what are known as stabilized grades. If you have ever seen a welded 300 series tank or whatever part, there is usually a thin region on either side of the weld that is "sensitized" and slightly rust colored. Sensitization occurs in the heat affected zone where the temp is between about 600-1200F during welding or other heat operations. Sensitization is officially where the Carbon in the metal combines with the Chromium to form Chromium Carbides, thus causing a locally depleted Cr content in that area. Stainless gets its corrosion protection from the Cr dissolved in solution in the metal - not as Chromium Carbides.

Type 321 and 347 are called stabilized because they are not susceptible to sensitization. This is accomplished by using slight alloy additions of Titanium (for 321) or Columbium (for 347). Either of these are stronger carbide formers than the Cr, so you can not form Chromium Carbides.

The sensitization problem cannot be fixed unless you heat treat the whole assembly up after welding if you do not use the 321 or 347 stabilized grades. Welding is also what 304L is made for, it has extra low carbon, so you have less carbon potentially available to combine with the chromium. Not as good as the stabilized grades, but better than 304 or 316.

 

[lilredex]

In general, yes. For stainless steels, there are basically 4 types commercially avalailable.
1) 300 series, also called austenitic stainless. Most common you will find or run into. These are the best for corrosion. The common numbers you might see are 304, 304L, 316, 308, 303, 302. These all have about 17-18% Cr and also have about 6-8% Ni. The Ni makes them non-magnetic. Common used for silverware and cooking or food prep. Cannot be heat treated to make stronger, but can be work hardened to bring strength up. Used mostly for superior corrosion resistance.
2) Martensitic stainless. These are 10-12% Cr and not much else for alloying. Commonly used for exhaust systems on factory systems, and other less harsh environments. These are magnetic and can also be heat treated to make stronger. Such as cutting blades. Typical numbers you might find are 410, 440.
3) Ferritic stainless. Second most common commercially available, they are also magnetic. More likely to find around marine or other wet environments where they don't want as much cost as the 300 series. Not as good corrosion resistance compared to 300 series, but better than 400 series. Typical numbers are 409 and 430
4) Precipitation Hardening (PH) stainless. These are used where high strength is needed. Magnetic also, but pretty good corrosion resistance. Since they require heat treatment and precipitation hardening for max strength you need to design around this. Most costly to buy and process. They have 15-18% Cr and 4-5% Ni as main alloy elements. Typical numbers are 17-4PH and 15-5PH.

Thank-you for your concise explanation. I have it copied and saved. Used to work in the manufacturing end of control valves and we regularly used 316, 416, and 17-4PH for valve trim.