Is All Stainless Steel Equal? 

Stainless steel is a general term for corrosion-resistant steel that contains a minimum of 10.5 percent chromium. Varying additions of nickel, molybdenum, titanium, niobium, and other elements may also be present. The mechanical properties and behavior of various types of steel depend on their composition. Choosing the appropriate steel grade is vital to success in any application.[1]

Looking at two types of stainless steel 

For our purposes, we’re focusing on ferritic and austenitic stainless steels, although there are several types (Figure 1). Ferritic stainless steels are plain chromium stainless steels, usually with low carbon content. They are magnetic and have good ductility and resistance to corrosion and oxidation. They are generally resistant to stress corrosion cracking.[2] Ferritic stainless steel shares some traits with austenitic stainless steel but contains no nickel, which makes it less expensive to manufacture. This allows for a lower-cost chimney pipe.

Austenitic stainless steels contain chromium and nickel with very low carbon content. They are non-magnetic but can become slightly magnetic when coldworded. Cold working also enhances their strength. Austenitic stainless steels have excellent corrosion resistance and good formabilit, weldability, and mechanical properties over a wide range of temperatures.[3] Adding nickel increases its corrosion resistance but also adds to the cost of the material.

Figure 2 shows us how austenitic stainless steels, 304 and 316, match up against ferritic stainless steels.[4] The chart shows us that 304 has better corrosion resistance than 430, but 316 is an even better choice for use with corrosive materials.

How different attributes are achieved 

Stainless steel grades 304L, 316L, and 316Ti have altered compositions to achieve different attributes. In the case of 304L and 316L, the carbon has been reduced. Carbon strengthens austenite, so it is a useful alloying element in stainless steels used in applications like boiler tubes, which operate at high temperatures. Carbon has no other useful function and can reduce corrosion resistance under certain circumstances.[5] A titanium-stabilized version (316Ti) of 316 is sometimes used in components that require elevated temperature strength and corrosion resistance, such as flexible chimney liners.[6]

Comparing pipe

When deciding which chimney to purchase, it’s important to consider your budget and what fuel you will be burning. In most applications, 430 will do an excellent job and is cost-effective. Sometimes, however, you need a higher-grade stainless steel, such as when burning coal. This Pipe Comparison Chart shows you what type of stainless steel different manufacturers use for their pipes.

Woodstovepro.com carries M&G Duravent DuraTech and DuraPlus, Metal Fab TempGuard, Security Chimney Secure Temp and Selkirk UltraTemp, GalvaTemp and SuperPro.

If you have any questions, please leave a comment or send us an email. We are always happy to help.

Written by Sean Summers, National Fireplace Institute (NFI) Master Hearth Certified Technician - WoodStovePro.com

1. British Stainless Steel Association - SSAS Information Sheet No.1.1 – March 2001
2. The Southern Africa Stainless Steel Development Association (SASSDA) website
3. The Southern Africa Stainless Steel Development Association (SASSDA) website
4. International Stainless Steel Forum (ISSF) – The Ferritic Solution: Properties, Advantages, Applications – 2007
5. International Molybdenum Association (IMOA) – Practical Guidelines for the Fabrication of High Performance Austenitic Stainless Steels - 2010
6. Australian Stainless Steel Development Association (ASSDA) website