ss 304 vs ss316L

The answer is not simple for such a broad question, but here are two links that will help you focus in on exactly what you need to know.

http://www.azom.com/Details.asp?ArticleID=863

http://www.azom.com/Details.asp?ArticleID=965

I will try to give you the data - Just google it ---you will find all sorts of information---Chrome content may be related to corrosion resistance

304

316L

You have not provided any information about where and how you intend use it--------Any way 316L is better for corrosion resistance---based on Nickel, Chrome and Molybdenum. Service life depends upon temperature, load and operational conditions. I suggest you pick 316L-------Also apply corrosion resistance coatings to extend life of material

Careful - while 316 is usually a better choice for corrosion resistance than 304 - it is not always the case - particularly in highly oxidizing acids such as nitric acid, and in pulpmill digester liquors where the higer chromium content of 304 performs better than 316 (even with molybdenum)

?!?!?!?! Why the @%$#@ would some one rate this comment as off-topic?!?!?!?!

If you don't believe these statements please refer to:

Page 24 of this document:

http://www.valve-world.net/pdf/11025.pdf

And this document

http://www.upmet.com/media/316-317.pdf

If you are too ignorant or proud to admit that 304 can better than 316 than ..............

Now, after ranting - I wonder if it was rated offtopic because I "forgot" to say 304L and 316L? In any case, I sometimes wonder why I even bother to try and help some people.

That's better - the "off-topic" vote is gone now. Thanks for the understanding.

Folks,

I have gathered some more information: (Requester did not give operating conditions----which is not good)

304/304L
Chemical Composition %

AVAILABILITY
Seamless Pipe 1/4" - 20"
Weld Pipe 1/2" - 24"
Butt-Weld Fit. 1/2" - 24"
Butt-Weld Fit. 1/2" - 12"
Pressure Fittings 1/4" - 4"
150# Fittings/Nipples 1/4" - 4"
Valves 1/2" - 24"
Tubings 1/4", 3/8", 1/2", 3/4", 1"
Flanges 1/2" - 24"
Bar 1/8" - 12"

SPECIFICATIONS
ASTM
A312, A376, A358, A269, A249, A403, A182, A351
ASME
SA312, 5A376, SA358, SA269, SA249, SA403, SA182, SA351

DESCRIPTION
304 stainless is a low carbon (0.08% max) version of basic 18-8 also known as 302. Type 302 has 18% chromium and 8% nickel. Type 304 has slightly lower strength than 302 due to its lower carbon content. Type 304 finds extensive use in welding applications because the low carbon permits some exposure in the
carbide precipitation range of 800 0 F - 1500 OF without the need for post-annealing operations. However, the severity of corrosive environments may necessitate annealing after welding or the use of 304L. Type 304L has a carbon content of 0.03% or less. This alloy can be used in the as-welded condition without becoming susceptible to intergranular corrosion.

DESIGN FEATURES
Oxidation resistance up to 1650 0 F for
continuous service and up to 1 1500 deg.F where cyclic heating is involved.
General purpose corrosion resistance.
Non-hardenable except by cold working.
Non-magnetic except when cold worked.
May be susceptible to chloride stress corrosion cracking.
Used where field working is employed.

TYPICAL APPLICATIONS
Sanitary
Dairy and Food processing
Heat exchangers, evaporators
Feedwater heaters

TENSILE REQUIREMENTS
Tensile Strength (KSI) 70
Yield Strength (KSI) 25

316/316L
Chemical Composition %

AVAILABILITY
Seamless Pipe 1 /4" - 20"
Weld Pipe 1/2" - 24"
Butt-Weld Fittings 1/2" - 24"
Butt-Weld Fittings 1/2" - 12"
Flanges 1/2" - 24"
Pressure Fittings 1/4" - 4"
150# Fittings/Nipples 1/4" - 4"
Valves 1/2" - 24"
Tubings 1/4", 3/8", 1/2 3/4", 1"
Bar 1/8" - 12"

SPECIFICATlONS
ASTM
A312, A376, A358, A269 A249, A403, A182, A351 A479, A276
ASME
SA312, SA376, SA358, SA269, SA249, SA182, SA276, SA403, SA479, SA351

DESCRIPTION
Type 316 is a molybdenum steel possessing improved resistance to pitting by solutions containing

chlorides and other halides. In addition, it provides excellent elevated temperature tensile, creep and stress - rupture strengths.

DESIGN FEATURES
• Type 316 is more resistant to atmospheric and other mild environments than Type 304. It is resistant to dilute solutions (i.e. 1-5%) of sulfuric acid up to 120 deg.F. However, in certain oxidizing acids, Type 316 is less resistant than Type 304.
• 316 is susceptible to carbide precipitation when exposed in the temperature range of 800 deg. - 1500 deg.F. and therefore is susceptible to intergranular corrosion in the as-welded condition.
• Annealing after welding will restore corrosion resistance.
• Type 316L has the same composition as Type 316 except the carbon content is held below 0.03%. Not unexpectedly, its general corrosion resistance and other properties closely correspond to those of Type 316. However, it does provide immunity to intergranular attack in the as-welded condition or with short periods of exposure in the temperature range of 800 deg. - 1500 deg.F. The use of 316L is recommended when exposure in the carbide precipitation range is unavoidable and where annealing after welding is not practical. However, prolonged exposure in this range may embrittle the material and make it susceptible to intergranular attack.
• The maximum temperature for scaling resistance in continuous service is about 1650 deg. F. and 1500 deg.F. For intermittent service.
• May be susceptible to chloride stress corrosion cracking.
• Non-hardenable; non-magnetic in the annealed condition, and slightly magnetic when cold worked.
• Improved corrosion resistance to chlorides.

TYPICAL APPLICATIONS
Nuclear, chemical processing, Rubber, plastics, pulp/paper, pharmaceutical and textile industries, heat exchangers, condensers and evaporators

TENSILE REQUIREMENTS
Tensile Strength (KSI) 70
Yield Strength (KSI) 25
KSI can be converted to MPA (Megapascals) by multiplying by 6.895.

Reference: http://www.rjsales.com/techdata/alloys/316.html

The main difference in terms of composition is the Molybdenum content of SS 316. teh conc of Mo is between 2/3 % and this gives to the 316 higher corrosion resistance particurarly in environments containing chlorides. This does not mean that 316 is immune to attack from chloride but that it can be used in fluid with higher conc of Cl-. For example in water usaully a safe limit for 304 is 200 ppm of Cl while for 316 is 500-1000 ppm. The pitting and crevice temperaure for 316 are higher (316 has an higher PRE -pitting resistance equiavlent) while regarding SCC (stress corrosion cracking) there is no difference between the two materials.

http://www.heiseymechanical.com/10087.pdf

The difference can also be partly attibuted to usage. 304 can be found commonly as sheet, plate, angle, etc. 316 is more likely to be found as pipes, valves, fittings, etc.

Generally, it is more economical to make large items in 304 where a general stainless steel is required, whereas items that come into intimate contact with exotic fluids and demand a higher level of corrosion resistance will benefit from the application of 316; these items are usually smaller than structures in 304.

"Horses for courses" - anon.

There are several websites on the application of stainless steels on the web, and a search engine will yield many hours of interesting reading material.

Basicly nthe ndiference in applications os:

The 316L has over protection for corrotion and heat application