General terms and conditions…


Core steel grade

Chimney systems manufactured by our company are made entirely of stainless steel. We use austenitic stainless steel, acid-resistant and ferritic stainless steels in our products.

Stainless steel – this is a group of steels that have special physical and chemical properties, resistant to corrosion due to e.g. weather conditions, diluted acids, alkaline solutions. Stainless steel is mainly composed of iron and chromium which gives stainless steel its outstanding resistance to corrosion. The higher the chromium content, the greater the resistance to corrosion.

For our chimney systems we use a core of austenitic stainless steel grade 1.4404 (AISI 316L) – for the Premium system (except for the MK PS) and ferritic steel grade 1.4521 (AISI 444) – for the Standard system.


Truths and myths about ferritic steels

 1. Ferritic steel is cheaper than stainless steel or acid-resistant steel.

 True, but… this is how it is. The above is a result of global speculation on nickel prices which fluctuate. Currently nickel prices have risen, so 4301, which has a lot of nickel, is more expensive. In the past this varied. The base price of our 4521 steel is and always has been approx. 35% higher than that of 4301. On the other hand, alloying causes the complete price for 4521 steel sheets to fluctuate, sometimes higher and sometimes lower than 4301. We use 4521 steel not because of its lower price but, as could be seen, for example in 2010, until May 2011 a steel sheet of 4301 was still cheaper (in terms of base plus alloying), then the prices drew level and then, because of speculation on nickel, and 4301 began to be more expensive. Using 4521 gives us the advantage that we can offer stable prices, as we are not dependent on price fluctuations.

2. It is created on the basis of ordinary black steel.

False. 4521 steel is stainless steel and additionaly acid-resistant, unlike 4301 which is only stainless steel but not acid-resistant.

3. This material is used only by MK Żary.

Truth.  We are proud of this. Because of its low nickel content this steel is less plastic and other manufacturers often encounter problems with it (it often breaks during processing) or there are problems with welding. We have successfully developed a unique technology for processing this steel grade.

4. This is obviously a much lower quality material.

False. This is a material that is not only stainless, but also acid-resistant. It should be noted that this steel grade has a resistance class V2, while 4301 does not. We have performed costly corrosion testing and V2 is a great result. Vm is the class given to 4301. As we were informed at the MPA institute, 4301 has no chance to pass the test for class V2.

5. 4301 is better than 4521 because other manufacturers also use it.

False. Other manufacturers started to use 4301 because it is cheaper than 4404 acid-resistant steel. However, replacing acid-resistant steel with ordinary stainless steel significantly reduces the quality. MK Systemy Kominowe replaced the acid-resistant 4404 steel with another, also acid-resistant steel.

6. Problems will appear after a few years in the case of a chimney made from 4521 steel.

False.  We have been using 4521 for 6 years (since 2007) and have had no complaints. In addition, this steel has been used in other industries for years, often in environments more conductive to corrosion than chimneys (in silencers in the automotive industry, extractor hoods in industrial kitchens, in the drums of washing machines).

7. MK knows that 4521 steel is inferior and often does not inform customers of this fact.

False. We are proud of this steel, we have never concealed the material from which our chimneys are made (it is in every catalogue, brochure, etc.)

8. Ferritic steel is worse because magnets stick to it, while they do not to stainless steel.

False. The sticking of a magnet has never been a measure of the quality of steel. This is another myth that steel that “catches a magnet” is in any way worse.

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