The influence of chromium on steel

img25The influence of chromium on steel

The influence of chromium on steel. Steels containing chromium in an amount up to 6% exhibit greater corrosion resistance than chromium-free steels. Even the content below 1% Cr in steel increases its corrosion resistance, especially in urban and rural atmosphere. With the content 3% of chromium, corrosion resistance in an industrial atmosphere increases by approx. 4—5 times compared to unalloyed steels. Special steels, containing more than 13% chromium, they are resistant to atmospheric corrosion. The resistance of these steels is due to the spontaneous formation of an oxide protective layer ,on their surface. The country produces approx. 20 types of corrosion-resistant steels. They are divided into three groups: martensitic steels, ferritic steels and austenitic steels. The resistance of these steels to clean atmospheres, containing no contamination with chlorides or sulfur dioxide is high, because they do not corrode at all in these atmospheres and their surface is rust-free even after several years of storage. However, if products are stored, e.g.. made of 4H13 steel, with high mechanical properties, containing 12-14% chromium and 0,35-0,45% C in an industrial atmosphere, then you should take into account the presence of rust on the surface of this steel, even though it is commonly called stainless steel. The sea atmosphere is also corrosive to stainless steels, which over time become covered with corrosion products. Containing steel behaves well in this atmosphere 18% chromium and 8% nickel, i.e. the so-called. corrosion-resistant steel. The highest resistance to weather conditions is demonstrated by acid-resistant steel 18/8 with the addition of molybdenum. The corrosion resistance of high-alloy steels is highly dependent on the smoothness of the surface. The best results are obtained by electrolytic polishing of steel after prior mechanical polishing that removes all macro surface irregularities.