Study On Atmospheric Corrosion And Corrosion Mechanism Of Low Carbon Alloy Steel Gears

Atmospheric corrosion of steel materials is a typical electrochemical corrosion.The main influencing factor is the thickness of the water film layer on the surface of the parts.The thickness of the water film layer mainly depends on atmospheric humidity,temperature,environmental media and mutual coupling.Aiming at the typical inland climate with high air humidity,high temperature and large temperature difference in summer in Xi’an,this topic discusses the relative humidity,temperature,water quality and other factors of the atmosphere by simulating the storage environment of synchronizer parts and carter parts in Xi’an in summer.The impact of atmospheric corrosion of various parts,combined with the surface corrosion rating of the sample,the corrosion product morphology and elemental energy spectrum analysis,to discuss the influence of different factors on atmospheric corrosion of parts,establish a model mechanism for atmospheric corrosion of steel parts,in order to provide effective references and suggestions for the factory to improve the corrosion phenomenon of low-carbon alloy steel parts during storage.Research indicates:At present,the cleaning agent and anti-rust agent selected by the factory have good anti-rust effect,and the anti-rust effect of the solution using the existing tap water configuration is basically the same as that of the deionized water configuration.In the static full immersion corrosion experiment,the synchronizer and the carter sample were completely corroded,and the surface was first produced a gray-green rust product,which was then converted into reddish brown hydrated ferric oxide.As the relative humidity of the air gradually increases from 75%,95%,and 98%to 100%RH,the corrosion law of the synchronizer parts is firstly increased and then decreased.Among them,the time required for 98%RH parts to reach the third level The corrosion time is 0.2h,and the corrosion is the most serious.The corrosion time under other humidity conditions is 380h,0.4h and 0.8h,respectively.However,carter parts are more sensitive to the relative humidity of the air,showing that the corrosion rate increases synchronously with humidity.The effect of relative humidity on the atmospheric corrosion of parts has a corresponding relationship with the thickness of the water film,indicating that atmospheric humidity mainly controls the degree of corrosion by affecting the thickness of the water film on the surface of the part.In the tidal atmosphere,the greater the relative humidity,the greater the thickness of the water film.The greater the corrosion current density of the electrochemical reaction,the more serious the corrosion;the wet atmosphere stage,the greater the humidity,the thicker the water film,but it also affects the dissolution and diffusion of oxygen atoms to the surface of the part,reducing the degree of atmospheric corrosion.Under constant humidity and constant temperature conditions,when the ambient temperature is 30℃,40℃ and 50℃ in sequence,with the increase of temperature,the corrosion rate of the synchronizer sample is positively correlated with the ambient temperature,and the cleaning agent and rust inhibitor can reduce the temperature effect.Carter parts also rose first,but after 40℃,the corrosion rate changes basically stable.Under constant humidity,the increase in ambient temperature will increase the thermal energy of the atoms in the metal,thereby accelerating the reaction rate and accelerating the occurrence of atmospheric corrosion;however,in the actual environment,when the factors of temperature and atmospheric humidity are coupled with each other,the parts Atmospheric corrosion is still determined by the thickness of the surface water film.Compared with the constant humidity constant temperature experiment,when the air humidity is 95%RH,the temperature is maintained at 50℃ for 1h and then reduced to 12℃ for 1h for variable temperature treatment.When the corrosion time is 2 hours,the temperature change treatment reaches three levels of corrosion time is 1h,Which is 50%under constant temperature.Explain that atmospheric corrosion is to control the degree of corrosion by coupling the temperature difference and relative humidity to form a complete water film thickness on the surface of the part.The atmospheric corrosion of parts is a typical appearance of oxygen concentration corrosion.First,the water film formed on the surface of the part acts as an electrolytic cell,Fe dissolves,and the edge of the water film acts as a cathode to reduce oxygen.As the corrosion continues,the Fe2+produced by the anode meets the OH-produced by the cathode,forming a corrosion product film Fe(OH)2.Fe2+ in the anode area formed granular γ-FeOOH deposits.However,γ-FeOOH appears as yellow rust with dot distribution.When corrosion continues,cell-like corrosion products are formed in the center of the droplet,that is,Fe3O4 black rust with a larger area and a deeper thickness.When the degree of corrosion is 3,the maximum depth of corrosion can reach about 20μm.Based on this,the article finally proposes that for the summer environment in Xi’an,the environment in which the factory stores parts should strengthen dehumidification and ventilation treatment.At the same time,the relative humidity and temperature difference are coupled with each other.When the temperature difference between morning and evening is large and long-term storage,the requirements for atmospheric relative humidity are lower.It is recommended that the relative humidity in the environment should not exceed 75%.