الفهرس 
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Abstract
Corrosion is a very important phenomenon that is responsible for damage for buildings, factories and bridges. Accordingly, a big ware is bayed in modern design for corrosion and development of materials that resist corrosion become very important as the most disaster occurs as a reason for corrosion. The aim of the present investigation is to improve the corrosion resistance of gray cast iron in H2SO4 acid. This is done by adding alloying elements that may increase corrosion resistance that may use instead of stainless steel. The investigation is done by evaluating the weight loss, microstructure and mechanical behaviour of medium chromium aluminium alloy, silicon gray and manganese nickel cast iron. The effect of immersion duration on corrosion behaviour of such alloys was investigated. The results revealed that one of the medium chromium aluminium alloys cast iron (ZI Cr28) having a chemical composition of 0.5-1 C%, 0.5-1.3 Si%, 0.4- 0.8 Mn%, 30 Cr%, and 4 Al%, exhibited better corrosion resistance against H2SO4 with a concentration of 98.9 which near to the corrosion resistance of the stainless steel. All chemical compositions have a dendritic structure, but the medium chromium aluminium alloys cast iron (ZI Cr28) exhibited very fine grains microstructure. The Silicon gray cast iron (Zl Si15 Mo3.5) alloy introduced larger grain size compared to ZI Cr28 and the graphite separate in form of flakes. The manganese nickel cast iron (ZI Mn8Ni) exhibited non-homogeneous microstructure. The ZI Mn8Ni alloys exhibited higher hardness values when compared with the other alloys particularly the alloy that contains 2.8-3.2 C%, 2-3 Si%, 7-9 Mn%, and 3 Ni% has the maximum value of hardness.