Electrochemical Performance Study of Rust Layer on Cu-P-RE Weathering Steel

Corrosion rates of 10PCuRE steels with different rate earth contents and plain carbon steel were studied by dry-wet cycle immersion test. The corrosion resistance of rust layer on rare earths weathering steel and carbon steel was studied through the electrochemical means of polarization test and electrochemical impedance spectra. The difference of corrosion resistance of testing steels was analyzed through electrochemical means. The 10PCuRE steels whose rare earths content is smaller than 0.016% have good performance of corrosion resistance because corrosion potential of the steel is positive and resistance of rust layer is large. The results showed that rare earths of proper content could diminish corrosion tendency and promote the formation of the steady and compact rust layer.

Multi-performance evaluation of high-throughput accelerated corrosion test for high-strength low-alloy 921A steel

The corrosion behavior of high-strength low-alloy 921A steel in a simulated marine atmospheric environment was studied using a high-throughput experimental method.The corrosion behavior,corrosion morphology,and corrosion products of 921A steels were analyzed using various techniques,including corrosion mass loss method,polarization curve,white-light interferometry,scanning electron microscopy,energy-dispersive spectrometry,microbeam X-ray fluorescence spectrometry,X-ray diffraction technique,and X-ray photoelectron spectroscopy.The test results indicated that 921A steel exhibits better corrosion resistance than Q450NQR1 steel in simulated harsh atmospheric environments,as evidenced by a lower corrosion mass loss rate throughout the corrosion tests.The corrosion products of both steels consisted ofα-FeOOH,Fe_(3)O_(4),andγ-FeOOH,withα-FeOOH being more prevalent in the rust layer of 921A steel than in Q450NQR1 steel.The inner rust layer of 921A steel also exhibited an appositional enrichment region of Cr,Ni,Mo,and V,leading to its superior corrosion resistance compared to that of Q450NQR1 steel.The efficacy of high-throughput accelerated corrosion experimental methods was highlighted for evaluating the corrosion resistance of steel materials in harsh environmental conditions.The findings suggest that 921A steel exhibits better corrosion resistance compared to Q450NQR1 steel and has the potential to be more suitable in harsh marine atmospheric environments.The characterization of the rust layer structures and composition reveals the parallel enrichment of certain elements in the inner rust layer of 921A steel,which enhances its corrosion resistance.

Effect of La on the Corrosion Behavior and Mechanism of 3Ni Weathering Steel in a Simulated Marine Atmospheric Environment

The corrosion behavior and mechanism of 3Ni weathering steel in a simulated oceanic atmospheric environment are investigated in order to comprehend the impacts of La,as determined through electrochemical analysis and rust layer characterization.The results of this study demonstrate that the addition of La enhances the corrosion resistance of 3Ni weathering steel in the marine atmospheric environment,thereby reducing the corrosion rate and improving the protection of the rust layer.The influence of La on corrosion resistance can be attributed to two primary factors.Firstly,La functions as a grain refiner,minimizing the potential difference of the micro-regions on the substrate surface,thereby significantly reducing the corrosion of bare steel in the marine environment.Secondly,La inhibits the process of Fe_(3)O_(4) oxidation back toγ-FeOOH during corrosion at the local site,thus decreasing the formation ofγ-FeOOH and enhancing the charge transfer resistance.This research work may serve as a reference for expanding the application of rare earth elements in the field of weathering steel.

Evolution of the Rust Layers Formed on Carbon and Weathering Steels in Environment Containing Chloride Ions

To clarify the correlation between alloy elements and growth pattern of the rust layers, the rusting evolution of the carbon and weathering steels was investigated by using the gold markers method. The corrosion experiments were carried out in a simulated environment containing chloride ions. The results indicate that Ni, Cu, Cr and Mo elements in the weathering steel suppress the rust crystallization and impede the rust layer growth to an internal development, and the suppression function benefits the formation of a protective rust layer. Moreover, c-FeOOH is mainly located in the outer rust layer, while b-FeOOH is mainly located in the inner rust layer, and the distribution of the rust compounds in the rust layer is closely related to the growth pattern of the rust layer.

Corrosion Behavior of Rusted 550 MPa Grade Offshore Platform Steel

The corrosion behavior of a rusted 550 MPa grade offshore platform steel in Clcontaining environment was investigated.The results revealed that the corrosion process can be divided into initial stage in which corrosion rate increased with accumulation of corrosion products and later stage in which homogeneous and compact rust layer started to protect steel substrate out of corrosion mediums.On the contrary,structural analysis of rust layers by X-ray diffraction showed that α-FeOOH increased from 1.3% to 3.6% and the Fe3O4 increased from 1.0% to 1.5% while γ-FeOOH reduced slightly according to corrosion time increased from 30 cycles to 73 cycles.The results of electron probe microanalysis indicated that Cr concentrated mainly in the inner region of the rust,inner/outer interface especially,whereas Ni and Cu were uniformly distributed all over the rust after 73 corrosion cycles.According to electrochemical measurements,it was found that the corrosion rate of rusted steel reduced from 0.61 mm/a after 45 cycles to 0.34 mm/a after 85 cycles,44.3% reduction approximately,and Rrust values increased with increment of corrosion time.Therefore,formation of compact inner rust layer and enrichment of Cr are important to improve corrosion resistance of offshore platform steel.

Characterization of Compactness of Rust Layers on Weathering Steels by an Adsorption/Dehydration Test of Ethanol

A new method for evaluating the compactness of rust layers on steels has been proposed in the present study. The method includes adsorption and dehydration process of anhydrous ethanol. The protective ability of rust layers can be qualitatively reflected by the adsorption/dehydration rates. The specific surface area and porosity of rust layers can be calculated by a quantitative model. The results from the present method are consistent with electrochemical tests, N2 adsorption and X-ray diffraction analysis. The method characterizes the compactness of rust layers rather than that of corrosion products removed from the metal surfaces, which is generally practiced in classic N2 adsorption method. Furthermore, the method can reflect the compactness of inner rust layers, to which N2 adsorption is unavailable. The method provides a new approach for the study of rust layers.

Effect of trace boron on corrosion resistance of rust layer of high-strength low-alloy steel in 3.5 wt.% NaCl solution

The influence mechanism of trace boron on the corrosion resistance of high-strength low-alloy(HSLA)steel in a simulated marine environment was studied by combining first-principles calculation with experiment.The effect of boron on the corrosion properties and corrosion morphology of the rust layer formed on the surface of HSLA steel was studied by means of corrosion weightlessness method,polarization curve,scanning electron microscopy(SEM)and X-ray diffraction(XRD)technique.The mass loss measurements and polarization curves revealed that the corrosion resistance of HSLA steel is improved by adding trace boron.XRD and SEM results show that the rust layer is produced byα-FeOOH(the main protective phase),Fe_(3)O_(4) andγ-FeOOH,and boron contributes to stability ofα-FeOOH.Based on the first-principles calculation,the solid solution of B atom in the corrosion product is beneficial to the fixation of Cl atom and to the reduction of the corrosion of Cl atom to the steel matrix.

A Study of Rust Layer of Ultra-Thin Cast Strip Steel Containing 0.10%Sb in Simulated Industrial Atmosphere

A new type of steel containing Sb based on the CASTRIP process had been designed to improve the corrosion resistance of high-strength steels in industrial atmospheres.The properties of the electrochemistry and rust layer(RL)were analyzed to evaluate the corrosion resistance of the ultra-thin cast strip(UCS)steel containing 0.10%Sb.Experimental results showed that the corrosion resistance of UCS steel containing Sb was doubled compared to that of traditional hot rolling strip(HRS)steel.It could be interpreted as an integral effect of CASTRIP process and alloying elements.The optimization for microstructure and inclusion of UCS steel can reduce the localized corrosion effects in initial corrosion processes.Cu,P and Sb reduced the anodic reaction and CuFeO2/Cu2O,CuO,FePO4 and Sb2O3 were formed,promoting the transition fromγ-FeOOH toα-FeOOH.A(Cu,Sb,P)-enriched inner RL was generated and significantly improved protective ability of the RL.

Effects of Cr, Ni and Cu on the Corrosion Behavior of Low Carbon Microalloying Steel in a Cl^- Containing Environment

The effects of Cr, Ni and Cu on the corrosion behavior of low carbon microalloying steel in a CI- containing environment were investigated. The results revealed that the corrosion process could be divided into the initial stage in which the corrosion rate increased with accumulation of corrosion products and the later stage in which homogeneous and compact inner rust layers started to protect steel substrate out of corrosion mediums. The results of X-ray diffraction （XRD） indicated that the rust layers of the three-group steels （Cr, Cr-Ni and Cr-Ni-Cu steels） were composed of α-FeOOH, β-FeOOH, γ-FeOOH, Fe3O4 and large amounts of amorphous compounds. The content of amorphous compounds of Cr-Ni-Cu steel was about 2%-3% more than that of Cr-Ni steel. The results of electron probe microanalysis （EPMA） showed that Cr concentrated mainly in the inner region of the rust of Cr-Ni-Cu steel, inner/outer interface especially, whereas Ni was uniformly distributed all over the rust and Cu was noticed rarely after 73 wet/dry cycles. The addition of Cr and Ni was beneficial to the formation of dense and compact inner rust layer, which was the most important reason for the improvement of corrosion resistance of experimental steel.

Corrosion Resistance on High Strength Bainitic Steel and 09CuPCrNi After Wet-Dry Cyclic Conditions

The accelerated wet-dry cyclic corrosion tests have been carried out of a high strength bainitic steel and 09CuPCrNi. The results indicated that the corrosion resistance of 09CuPCrNi was better than that of the bainitic steel based on the mass loss measurements. The morphology and composition of the rusting products have been investigated in order to realize the mechanism of rust formation on the two steels. The rust scale on both steels was composed of a dense inner layer and a loose outer layer. The inner layer grew thicker and denser as the test proceeding. Both of inner and outer layers were mainly composed of magnetite （Fe3O4） and maghemite （γ-Fe2O3） with a small amount of lepidocrocite （γ-FeOOH） and akaganeite （β-FeOOH）. The rust phase of γ-Fe2O3 was detected in a higher amount of the inner layer, resulting in a much denser inner layer. The inner rust layer of 09CuPCrNi being denser and thicker than that of the high strength bainitic steel was attributed to the alloying elements such as copper, chromium and phosphorus enriched in it. The protective inner rust layer plays an important role in the corrosion resistance of the steel.

Influence of Alloying Elements on Mechanical Properties and Corrosion Resistance of Cold Rolled C-Mn-Si TRIP Steels

The rust layer plays an important role in the corrosion of steel in chlorinated environments. Salt spray, po- tentiodynamic polarization curve and tensile test were conducted in laboratory for the specimens after two-stage heat treatment. The influence of the alloying elements on mechanical properties and corrosion resistance of three kinds of steels was investigated by observing the microstructure and the morphologies of rust layer. The results show that the highest value （29%） of total elongation for steel A is obtained. The mechanical property of the specimen for steel C exhibits best strength ductility balance （21 384 MPa ·%） because of the presence of the multiphase microstructures after a two-stage heat treatment and the addition of the alloying elements. The corrosion products are known to be a complex mixture of Fe3O4 , Fe2O3 and α-FeOOH for steel C. The presence of the alloying elements results in the for mation of compact and dense rust layers in steel B and C. Passive film protects the substrate of TRIP （transformation induced plasticity） steel containing a complex mix of multiphase. Superior corrosion performance is exhibited for steel C with low alloying contents due to the enrichment of alloying elements within the rust layers.

Atmospheric Corrosion of Q235 Carbon Steel and Q450 Weathering Steel in Turpan,China

Q235carbon steel and Q450 weathering steel were exposed to the hot and dry environment of Turpan,China for three years.The corrosion rates of both steels were calculated and compared.The morphologies of the rust layer products were observed by optical microscopy and scanning electron microscopy.Analyses of the rust layers were performed by X-ray photoelectron spectroscopy,X-ray powder diffraction,and Raman spectroscopy,and analysis results indicate that the compositions of rust are main iron rich oxide such as FeOOH,Fe_3O_4,and Fe_2O_3.The iron oxide layer content proportion was calculated through a semi-quantitative algorithm.The resistance elements（Cr,Ni,and Cu）enhanced the resistance properties of the Q450 weathering steel matrix.Moreover,the resistance elements increased the proportion of goethite crystals in the corroded rust layer.

Industrial Atmospheric Corrosion Resistance of P-RE Weathering Steel

The corrosion behavior of low carbon steel （CS）, P-bearing steel （PS） and P-RE weathering steel （P-REWS） exposed for two years in Jiangjin of China was investigated. The results showed that during 2-year exposure test, corrosion data of the experimental steels followed the bilogarithmic equation, and the average corrosion depth of PS and P-REWS was decreased by 19.5% and 28.2% respectively compared with that of CS. Scanning electron microscope, electrochemical impedance spectroscope and Fourier transform infrared spectroscope were used to characterize the corrosion products. The research results showed that P in steel could promote the formation of an amorphous ferric oxyhydroxide layer near the substrate. The addition of RE could effectively increase the charge transportation re sistanee of rust.

Stabilization technology and corrosion mechanism of rust layer on Q370 weathering steel surface

A newly developed rust layer on Q370qENH weathering steel(sample C)was studied under dry–wet cycle test of 3.5 wt.%NaCl solution and salt spray test,compared with the bare weathering steel(sample A)and the weathering steel with additive contents(CuSO_(4)0.2,FeSO_(4)0.1,NaHSO_(3)0.02,NaCl 0.02,Na_(2)HPO_(4)0.01,and water balance,in mass%,termed as sample B).Corrosion mechanism of Q370qENH weathering steel after different surface treatments was investigated by means of surface potential scanning,mass change,polarization curve,and X-ray diffraction.The results of X-ray diffraction indicate that rust of bare weathering steel has rare Fe_(3)O_(4),and a dense oxide layer mainly composed of Fe_(3)O_(4) is formed on rust of both sample B and sample C.The surface potential of sample A gradually increases to−0.2 V in the dry–wet cycle test,while the surface potential of sample A maintains at about−0.6 V in the salt spray test.The surface potential of sample B and sample C is higher than that of sample A in the early stage and remains stable during the short-term accelerated corrosion test.Moreover,the mass change of sample C gradually stabilizes with time in the dry–wet cycle and salt spray test.The corrosion current of the sample A is lower than that of sample C in the initial stage of short-term accelerated corrosion test.However,the corrosion current of sample C is smaller than that of the sample A in the experiment.The main components of the deep rust of sample A areγ-FeOOH andα-FeOOH,while those of the deep rust of sample B and sample C are Fe_(3)O_(4).

Corrosion Behavior of High Performance Offshore Platform Steel with Chromium and Nickel Addition in the Environment Containing Chloride Ions

The characterization of corrosion products formed on a high performance offshore platform steel in the en- vironment containing chloride ions has been investigated by scanning electron microscopy （SEM）, X ray diffraction （XRD）, electron probe microanalysis （EPMA） and electrochemical impedance spectroscopy （EIS）. The results re- veal that the corrosion process can be divided into the initial stage and the later stage. The main constituents of rust layers are c~ FeOOH, 13-FeOOH, y-FeOOH, Fe：^（）~ and large amounts of amorphous compounds. With increasing corrosion time, the mass fraction of a-FeOOH and Fe：~ O,, increased, while that of y-FeOOH and ^-FeOOH changed slightly. The enrichment of Cr and Ni at the inner/outer interface, especially the side of inner rust, can be observed in the later corrosion stage of Cr Ni steel, which can promote the formation of compact inner rust layer, impeding the transmission of corrosion mediums and slowing down the electrochemical reaction process.

Study on the Corrosion Resistance of Multiphase TRIP Steels

Multiphase TRIP (Transformation Induced Plasticity) steels are known to combine higher strength with higher ductility.In this paper,the corrosion resistance of this steel has been has been investigated by accelerated corrosion tests,such as wet/dry cyclic corrosion and the weight loss in laboratory.The morphologies of their rust layers were observed by using scanning electron microscopy,and the corrosion performance of these steels was discussed by analyzing the protective mechanism.The results show that the corrosion rate of steel A is significantly greater than that of steels B and C in wet/dry cyclic corrosion and weight loss tests.The corrosion performance of conventional C-Mn-Si TRIP steel is deteriorated in both NaHSO 3 and 3.5 wt.% NaCl aqueous solutions.And superior corrosion performance is exhibited for TRIP steel with low alloying contents due to its high thermodynamic stability.The enhancement of corrosion performance of TRIP steel is attributed to the additions of alloying elements,such as Al,Cu,Cr,Mo,Ni,etc.The alloying elements increase the compactness of rust layers,so electrochemical characteristic of TRIP steel is improved.