Corrosion Behavior Of High-strength Corrosion Resistant Rebar In A Solution Of Chlorine Salt

In recent years,with the accelerated pace of China’s economic modernization,there are certain requests for the steel material in its high intensity and corrosion resistance and so on.The thesis used weathering steel and straight carbon steel as test objects,and corrosion behavior of the test materials was evaluated and analyzed by electrochemical method.The accelerated corrosion test of the test steels in laboratory was carried out by dry-wet circles test and salt spray test to explore the corrosion rulesof constituent in the condition of villaumite.The morphology and structure of the rust layer in different accelerated corrosions were measured by scanning electron microscopy and XRD diffractometer.The electrochemical results of the test steel showed that when over 0.7% of the Cr element was added to the steel,the anode would be "passivated" if the electrokinetic potentialis was polarized in the 3.5% Na Cl solution.With the increase of the Cr content,the range of passivation gradually increased,and its dimensional density gradually decreased.When Cr,Ni and other elements were added to the steel,the corrosion potential was overall high.With the join of Cr,Ni,Cu and other content,the tendency of steel corrosion was less and steel purity was higher,that is,the S,O content was less,and the corrosion current density was smaller,that is,the rate of corrosion of steel was slower.In addition,with the increase of the Mn content,the synergistic effect of Mn-Cu improved the density of rust layer and build up the boundary strength,thereby the corrosion rate decreased at the latter stage of corrosion.The dry-wet circles corrosion results of the test steel showed that with the decrease of C content in steel and the increase of Cr,Cu and Ni,the corrosion rate decreased obviously.The structure of rust layer was improved,the number of cracks and holes in the inner rust layer decreased,and the densification of the rust layer was enhanced,whose bonding strength with the basal body was upgraded.The synergistic effect of alloying elements restrained the generation of β-Fe OOH,γ-Fe OOH and Fe3O4,promoted the non-crystallizing of rust,and improved the composition of the rust,thus having increased mechanical properties and corrosion resistance.The salt mist corrosion results showed that When alloying elements like Cr,Ni,Cu and Mn were added in the steel,the beneficiation of those elements in the corrosion pit would generate refractory material to improve the corrosion resistance of the alloy.The corrosion resistance of rust layer was closely related with the structure of rust layer.At the beginning of the corrosion,the diffraction intensity of γ-Fe OOH was higher and that of α-Fe OOH was lower,so the overall corrosion rate of the α-Fe OOH / γ-Fe OOH was increasing at the beginning.In later period,γ-Fe OOH gradually transformed into α-Fe OOH,and γ-Fe OOH gradually disappeared.The ratio of α-Fe OOH / γ-Fe OOH increased rapidly,so the corrosion rate decreased rapidly.In summary,the thesis discusses the influence of the addition of alloying elements on the corrosion performance,and provides the basis for the design of the alloying elements of corrosion resistant steel.