chromium – increases hardness, corrosion resistance;
titanium – increases strength, corrosion resistance;
nickel – increases strength, ductility, corrosion resistance;
manganese – increases hardness, wear resistance, toughness;
molybdenum – increases strength, corrosion resistance at high temperatures.

Chrome provides stainless steel with corrosion resistance properties and a noble color. Corrosion resistance arises due to a film of chromium oxides that forms on the surface of the metal when it interacts with oxygen in the air, and is capable of self-repair after damage. The minimum chromium content in stainless steel is 11%. This class of steel (AISI 430) is called ferritic and is used only in low-aggressive environments or for the production of tableware and decor. This type of steel is not used for making chimney parts that come into direct contact with exhaust gases due to its weak corrosion resistance.

In addition to chromium, nickel, molybdenum, and titanium are used in stainless alloys. Nickel provides the alloy with ductility and viscosity. Chromium-nickel steels, which contain at least 8% nickel and 17% chromium, are called austenitic chromium-nickel (AISI 304). This type of steel has higher corrosion resistance at elevated operating temperatures (up to 450°C). Chromium-nickel steel is used in the production of chimneys with mandatory restrictions on the maximum operating temperature and the moisture regime of the gases being emitted.

Molybdenum and titanium increase the resistance to corrosion, inhibit the precipitation of chromium carbides, and enhance hardenability, even at high temperatures up to 800°C. This type of steel is called austenitic chrome-nickel-molybdenum (AISI 316) and is widely used for the production of chimneys. They are not susceptible to corrosion from aggressive condensate (water vapor + sulfur present in fuel = sulfuric acid) of flue gases at high temperatures.

The 200 series (AISI 201-202) is a nickel replacement using manganese, copper, and nitrogen. The nickel content in this product ranges from 1-4%. Due to certain properties, this grade is compared to the 300 series. It is non-magnetic, has low anti-corrosion characteristics, and does not meet international standards (AISI).

The most important property of stainless steel modular chimney systems is the metal’s chemical composition, which depends on the temperature of the flue gases from the heat generator (boiler, fireplace, stove).

Western and leading domestic manufacturers only use high-alloyed austenitic stainless steels. These steel grades are resistant to acidity and heat. This is a great opportunity for manufacturers to offer warranties of over 10 years on their chimneys.