Corrosion Experimental Study On X80 Steel Under Silt Soil Contaminated By Ammonia Water And Sodium Hydroxide

In this paper,through laboratory simulation tests,electrochemical impedance spectroscopy(EIS),polarization curve(PC),scanning electron microscope and other major testing and research methods are mainly used to study the corrosion behavior of X80 steel by two alkaline contaminated silt,sodium hydroxide and ammonia water,and reveal its corrosion mechanism.Through the electrochemical impedance spectroscopy(EIS)test and analysis of X80 steel,it is found that the corrosion law of X80 steel in ammonia contaminated silt is as follows: when the power is tested for 0h ~ 1h,the arc radius of low-frequency capacitive reactance gradually decreases with the increase of concentration;From 3h to 24 h,the radius of capacitive reactance arc gradually increases with the increase of concentration.The dielectric resistance Rs and the charge transfer resistance Rct generally show a decreasing trend with the increase of ammonia concentration.The charge transfer resistance Rct generally shows a decreasing trend with the increase of the electrifying corrosion time.For X80 steel in sodium hydroxide contaminated silt,the arc radius of low-frequency capacitive reactance gradually decreases with the increase of sodium hydroxide concentration at the same power-on time.The dielectric resistance Rs and the charge transfer resistance Rct generally show a decreasing trend with the increase of ammonia concentration.The charge transfer resistance Rct generally shows a decreasing trend with the increase of the electrifying corrosion time.From the polarization curve(PC)test of X80 steel in ammonia contaminated silt,itcan be concluded that the polarization curve moves to the right with the increase of concentration,and gradually moves to the left with the increase of concentration at higher concentration.The fitting results show that with the increase of corrosion time,the corrosion rate increases gradually at low concentration,and rises slightly in a small range at high concentration.The polarization curve test analysis of X80 steel in sodium hydroxide contaminated soil shows that the polarization curve moves to the right at low concentration(0.5%),the coincidence rate of polarization curve is higher at higher concentration(0.7%),and the polarization curve moves to the left at 1% for 1 h to 24 h after electrifying corrosion.The fitting results show that the corrosion rate increases gradually with the increase of sodium hydroxide concentration.From the macro and micro corrosion images of X80 steel,it can be concluded that the corrosion area of X80 steel is large in uncontaminated soil,and the corrosion products are piled up thick but not dense.In ammonia contaminated soil with concentrations of 0.5% and0.7%,the area of corrosion products is smaller than that of uncontaminated soil,and the corrosion degree of corrosion spots is uneven.At 0.7%,only a few points in the corrosion spots show more loose corrosion products and cracks.The corrosion area of X80 steel embedded in 1% ammonia contaminated silt is small,but the corrosion spot is uniform and the corrosion products are compact,and there is no shedding and protrusion phenomenon.In the 0.5% sodium hydroxide contaminated soil,the corrosion pits are relatively small and the corrosion products are relatively thin.At 0.7%,the corrosion pit is larger,the color is darker,and the corrosion products are piled up more,but there are a lot of cracks on the surface,which are not dense and have no obvious signs of falling off.When the concentration is 1%,the corrosion products are thicker,denser and smoother than before,and some points show slight signs of falling off and loosening.A comparative analysis of two alkaline contaminated soils shows that the impedance capacitive arc radius in ammonia contaminated soil is larger than that in sodium hydroxide contaminated soil.The polarization curve of X80 steel specimen in sodium hydroxide contaminated silt moves to the right than that of X80 steel in ammonia contaminated silt.The corrosion rate of X80 steel in ammonia contaminated silt is faster.At the concentration of 0.5%,the same rule as above appears at the initial stage of corrosion.However,as the duration of electrifying corrosion increases,the impedance spectrum radii of the two pollutants gradually approach coincidence,and the polarization curves also approach until coincidence.That is,when the concentration is 0.5%,after a period of electrifying corrosion,the corrosion rate of ammonia water and sodium hydroxide to X80 steel is basically the same.