Corrosion Resistance Investigation Of The Ni56Cr22Mo13Cu Alloy

With the development of industry, especially in the field of organic synthesis, and petrochemical manufacturing, increasing the probability of high-temperature, high-pressure, high-concentrations of harmful impurities or mixed into the corrosion and other harsh environment, all of the structural material of high corrosion resistance is proposed requirements. Nickel and Nickel-based corrosion resistant alloy is to satisfy the above-mentioned requirements ideal material. By the addition of copper, chromium, molybdenum and tungsten and other elements developed nickel-based corrosion resistant alloys, maintaining the good characteristics of nickel, but also a variety of alloying elements of both good performances. In the 1930s appear of Ni-Cr-Mo alloys, is through optimizing Ni-Cr and Ni-Mo alloy to form a class of alloys both resistance to oxidation acid and reducing acid.In order to guarantee the experiment with alloy microstructure uniformity, using vacuum induction furnace smelting mother alloys, Then using non-consumable vacuum arc melting to add different amounts of alloy Cu. Learning from other literatures, the best heat treatment process of Ni-based alloy for solid solution processing is that, quenching temperature 1150℃, time for 2.5 hours. Do the job according to this method. Adopt full immersion corrosion test method, inspection Cu volume on Ni-based corrosion resistant alloy corrosion resistant performance impact. Using different corrosive medium in this test, including: 80%H₂SO₄, 30%HCl, 80%H₂SO₄+5%Fe₂(SO₄)₃, 30%HCl+10%FeCl₃, acid mixture, 10%FeCl₃. The temperature of test is 90℃, and the test lasted 96h. Using scanning electron microscopy (SEM) and Energy Dispersive Spectrometer (XDS) to analysis the sample surface morphology and corrosion products, elaborated the material corrosion mechanism. It aims to probe the content of Cu's effect on the performance of electrochemical corrosion resistance. Adopt M283 electrochemical workstation to test normal temperature corrosion behavior of Ni56Cr22Mo13Cu respectively in the 80%H2SO4 solution and in the 30%HCl solution, get the corrosion potential and corrosion current parameters of Ni56Cr22Mo13Cu alloys in different corrosion media. The results show that, in 80%H₂SO₄, the Corrosion rate with the increase of the content of Cu decreased, when the content of Cu exceeds 3.2%, alloy corrosion rate increase. When 80% H₂SO₄ solution mixed with Fe³⁺, the corrosion rate reduced. In 30%HCl, the corrosion rate increases with the increase of Cu content becomes larger, when more than 3.2% of element Cu, the corrosion rate increasing trend became more apparent. When 30%HCl solution mixed with Fe³⁺, corrosion rate has ramped up. In 10%FeCl₃ solution, Added to the Cu in the alloys, can greatly improve the Pitting corrosion resistant ability. In the mixed acid, the alloy exhibits good corrosion resistance, the corrosion process is similar to alloys in oxidizing acid. Experiment proved that, when the content of Cu is about 3.2%, the Ni56Cr22Mo13Cu alloy has better overall corrosion resistance.From the polarization curve of Ni56Cr22Mo13Cu alloy in 80% H2SO4 solution, the passivity area can be found easily. The results from polarization curve Calculated, the alloy with more content of Cu can make passive current to be negative; this is more conducive to the passivity of alloy. In 30%HCl, the alloy corrosion current increases with the Cu content decreases, suggesting that, Cu can accelerate the speed of the material damage in HCl.