Pitting Resistance Research Articles

Microstructure and Corrosion Characteristics of Selective Laser-Melted 316L Stainless Steel: The Impact of Process-Induced Porosities

The microstructure and corrosion susceptibility of selective laser-melted (SLM) 316L stainless steel on planes aligned and perpendicular to the building direction in aqueous 3.5 wt.% NaCl solution were investigated and compared with their conventionally wrought counterpart. Cyclic potentiodynamic polarization results confirmed a superior pitting resistance and a reduced rate of metastable pitting for the SLM-fabricated samples regardless of the sample’s orientation compared to the wrought alloy. Although the process-induced porosities in the SLM samples did not affect the corrosion and pitting potentials of the alloy at the initial immersion time, they likely contributed to the reduced re-passivation potential of the surface. Furthermore, at longer immersion times, the electrochemical impedance spectroscopy and immersion testing results confirmed a more detrimental impact of the process-induced porosities on lowering the electrochemical stability of the SLM-316L surface perpendicular to the building direction, where larger size and higher density of crevice-like porosities were detected.

Microstructure, mechanical properties and corrosion resistance of CoCrFeNiWx (x = 0, 0.2, 0.5) high entropy alloys

In this study, the microstructures, microhardness, compression performance and corrosion resistance of CoCrFeNiWx (x = 0, 0.2, 0.5, denoted as W-free, W0.2, and W0.5, respectively) high-entropy alloys (HEAs) have been studied. Intensive studies show that W addition leads the severe lattice distortion, and thus aggravates the driving force of composition decomposition for W-free HEA. The dual-phase with face-centered cubic (FCC) microstructure in W0.2 and W0.5 HEAs was identified. In addition, a μ-(FeCoCr)7W6 phase precipitate from the matrix in W0.5 HEA. Moreover, the 11.12 at.% W addition induces the formation of cell dendrites and eutectic inter-dendrites with fine laminar spacing in W0.5 HEA. W addition obviously decreases the grain size, and enhances the microhardness and yield strength of W-free HEA. The W0.5 HEA has the high microhardness of 357.9 HV and yield strength of 556 MPa, while maintaining the reasonable fracture strain of 35.6%. The strengthening mechanism of mechanical properties can be attributed to the grain refinement strengthening, solid-solution strengthening, and interface hardening. The enhancements of the latter two strengthening effects depend upon the existence of dual FCC phases. The pitting resistance of the containing-W HEAs is enhanced in seawater solution compared with W-free HEA. Especially, the W0.5 HEA bears the best pitting resistance and easy passivation behavior, owing to that W addition improves the stability of the protective layer.

Influence of circulating waters’ parameters, chemical composition and structural heterogeneity of AISI304 steel on its pitting resistance

The goal of the work was to study the affect of the parameters of steel and circulating waters on the pitting resistance of AISI304 steel to develop practical recommendations for its use when manufacturing and operating heat exchangers. Based on the analyzed results of the study of how the AISI304 steel and circulating waters’ parameters affect its pitting resistance, there were plotted regression models: a first-order linear model, a second-order model, a second-order model with first order quotients, and a linear model with a reduced number of indications. The analysis of these models has shown that the pitting resistance of the steel in model circulating waters is most affected by its chloride content and the average distance between oxides in the steel. The indications x3 (average diameter of austenite grains) and x10 (Cr content) have a slightly lesser effect the steel’s pitting resistance criterion.

Corrosion resistance and morphological deterioration of 316Ti austenitic, GX4CrNiMo16-5-1 martensitic and 444 ferritic stainless steels in aqueous corrosive environments

The corrosion resistance of 316Ti austenitic, GX4CrNiMo16-5-1 martensitic and 444 ferritic stainless steels in 1 M H2SO4 solution at 0%–6% NaCl concentration was studied by potentiodynamic polarization, open circuit potential measurement and optical microscopy characterization. GX4CrNiMo16-5-1 exhibited the lowest corrosion rate result with optimal value of 4.073 mm/y compared to 316Ti and 444 steels with optimal values of 16.033 mm/y and 20.844 mm/y. The corrosion rate of GX4CrNiMo16-5-1 decreased with increase in NaCl concentration. GX4CrNiMo16-5-1 exhibited the highest pitting resistance at all NaCl concentrations, sustaining its passive film throughout compared to 316Ti and 444 steels whose passivity were lost at 1% and 2% NaCl concentrations. The OCP plots of GX4CrNiMo16-5-1 where significantly electropositive with significant positive displacement compared to 316Ti and 444 steel whose OCP values were electronegative. Optical morphological characterization of the steels shows the absence of localized corrosion deterioration on 316Ti though the steel generally corroded. 444 steel exhibited significant pitting corrosion compared to GX4CrNiMo16-5-1 with visible intergranular corrosion.

Design ambient-curable superhydrophobic/electroactive coating toward durable pitting corrosion resistance

The weak mechanical and chemical stability, poor pitting resistance and high-temperature curing condition still persist as major challenges for scale-up applications of most superhydrophobic coatings. To address these problems, an omnipotent ambient-curable superhydrophobic coating embedding with electroactive polyaniline/halloysite nanotubes (PANI/HNTs) was constructed in this work via facile spraying technique, using ethylene-(hydroxyl-alkyl) vinyl ether as film-forming material. Fluorinated SiO2/HNTs were fabricated and integrated into the coating matrix to create re-entrant curvature and nano/micro structured papillae in pursuit of high surface roughness. The resultant extraordinary superhydrophobic surface with water contact angle of 158.1° and sliding angle of 1.9° gave rise to prominent self-cleaning and anti-fouling abilities. The obtained strong adhesive strength, high durability to withstand mechanical challenges, superior chemical stability under corrosive media and especially pitting resistance at defect sites under hyper-salinity environment are assumed to ensure the long-term protection of metal substrates. Based on the electrochemical analysis, the protective mechanisms involving physical barrier function of binary superhydrophobic surface and passivation effect of PANI/HNTs nanofiller are proposed. The ambient-curable one-pot strategy in this work potentially opened up a new avenue for coatings with integrated functionalities, which present enormous application value under vigorous erosive/abrasive environment.

Modern ideas about pitting corrosion of corrosion-resistant steels and alloys

Purpose. To analyse, systematize and generalize modern representations about a pitting corrosion the alloying steels and alloys in the chloride-contacting environments.Methods of researches. The analysis of literary data according to the work purpose, comparative analysis, method of expert evaluations.Results. In particular, it has been shown that metastable and stable pitings, mainly, originate and develop in the vicinity of inclusions, which are composed of steels and alloys. Their nature and size directly affect the compressive strength of these structural materials. In addition, metastable pitings significantly pour on the intensity of growth of stable due to the redistribution of anode currents between them. At the same time, that they are larger and higher their number on the surface of the steel or alloy, then lower the anode currents in stable sweating and the speed of their growth. It is proved that in pitting metal dissolves selectively. As a result, in their vicinity solid phase diffusion of the main components of the alloy occurs, which leads to enrichment of the surface of metastable pitings with chromium, and stable iron. Because of this, metastable pitings are repatriated, and stable grow as a result of defect formation. Taking into account the characteristic features of selective dissolution of metals in metastable and stable pitings. It is proposed to identify them according to the coefficient of selective dissolution of Cr from pitings. In particular, if it is less than one, then the steel or alloy pits up with the formation of stable pitings, and, if greater, then metastable. It is shown that the chemical composition of steels and alloys also determines their pyrotechnic resis­tance in chloride-containing media. In this case, the most significant effect belongs C r, Mo, N. The positive influence of Cr and Mo on the compressive strength of corrosion-resistant steels and alloys is associated with mixed oxide films, which these chemical elements form on their surface. However, there is evidence that phosphorus contributes to the segregation of Mo and Cr atoms into the oxide film, and thus contributes to the growth of the compressive strength of these structural materials in chloride-contacting environments. At the same time, Cr contributes to increasing the solubility of nitrogen in a solid solution of austenite, which leads to the formation of ammonia complex in pitings, which reduces the pH of the corrosive medium in the pitting, that is why they are repacivated.Scientific novelty. Metastable pittings originate and develop before they are repaciated, when the cathodic reaction near the surface of steels or alloys occurs during oxygen depolarization, and stable – with oxygen and hydrogen on their surface as a result of hydration, dissolved alloy components in corrosion products.Practical value. The enterprises which make the heat-exchanging equipment working in the chloride-contacting reverse waters can choose optimal alloyed steels and alloys for their pitting resistance and to predict their corrosive behavior.

Semiconductor properties of passive film and corrosion resistance of 2205 duplex stainless steel joint welded by laser hybrid welding

Purpose There are obvious differences in corrosion resistance of different 2205 welding joints with different ratios of austenite and ferrite, from the top to the bottom, the austenite content decreased gradually while the ferrite increased. In each region of welded joint, the pitting resistance number of ferrite is higher than that of austenite; pitting corrosion is more likely to occur in austenite phase first on the top region of the weld and in the secondary phase precipitates on the other regions of the weld. The fluctuation of the ratio of austenite and ferrite has a great influence on performance of passive film in 3.5 per cent NaCl solution. Design/methodology/approach To study the corrosion behavior of welded joint, the samples were obtained by laser hybrid welding. Pitting corrosion was studied in different area of welded joint. The Mott–Schottky curves of welded joints were measured to study the passive film on the different welded joint area. Findings Due to the difference of heat input and the limit of filler depth of the wire, the microstructure of duplex stainless steel laser welding joint has obvious difference in the thickness direction. In addition, there will be harmful secondary phase (such as chromium nitride and σphase) precipitates in the lower part of the joint. For the welded joint, the corrosion resistance decreases with the increase in the difference of the microstructure. Pitting corrosion usually takes the two phases as the nucleation point and grows up. The surface of 2205 duplex stainless steel laser hybrid welding joint cannot form a complete passive film in 3.5 per cent NaCl solution, and the more the ratios of austenite and ferrite deviate from equilibrium position (50:50), the worse the performance of passive film is. Originality/value In this paper, the authors attempt to establish the correlation between the semiconductor electronic properties of passive film and the difference of microstructures and the component in a joint welded by laser hybrid welding. The effect of passive film on the corrosion resistance of the weld was further investigated.

On the pitting resistance of friction stir welded UNS S82441 lean duplex stainless steel

Friction stir welding has been considered as an alternative to fusion welding processes of stainless steels. A lean duplex stainless steel, grade UNS S82441, has been recently developed and is prone to localized corrosion, such as pitting when exposed to harsh conditions during use. However, pitting resistance of UNS S82441 has not been previously investigated. In this study, UNS S82441 lean duplex stainless steel was friction stir welded, and its microstructure and localized corrosion resistance were investigated by phase volumetric fraction, scanning electron microscopy, transmission electron microscopy and electrochemical tests. The pitting resistance of each zone was investigated by polarization tests and by determining the critical pitting temperature. The results indicated that microstructural changes promoted by friction stir welding affected the pitting resistance of the lean duplex stainless steel.

Electrochemical Changes with Thermal Aging of Duplex Stainless Steels

Duplex stainless steels are extensively used in pressurized water reactors (PWR) in the form of welds and castings (pumps, valves, etc.). Long-term thermal aging of duplex stainless steels leads to embrittlement due to α-αʹ phase separation in the ferrite grains and this phase separation results in degradation of the corrosion resistance of these alloys. This study investigated the effect of thermal aging time on the electrochemical and corrosion properties of as-received and thermally aged duplex stainless steels in a range of PWR water chemistries. The duplex stainless steels such as 2101, 2003, 2205 and welded 2101 and 2209, were subjected to electrochemical characterization in the as-received condition or after thermal aging for 100, 1000 and 10,000 hours. The electrochemical characterization constituted of open-circuit potential (OCP) monitoring, electrochemical impedance spectroscopy (EIS), linear polarization spectroscopy (LPR) and cyclic polarization (CP) in near neutral aqueous solutions, containing 2.2-5 ppm Li (LiOH) and 800-2000 ppm B (H3BO3). In addition, to investigate the effect of chlorides on the pitting resistance of these alloys, 1M concentration of chlorides (NaCl) were added to the base solution. The α-αʹ phase separation has been characterized by atom probe tomography, nanoindentation and impact toughness testing. The results indicated degradation in impact toughness and corrosion resistance with increasing aging time and phase separation. Some base cases were further characterized for microstructures and rust analysis using optical microscopy and scanning electron microscopy. The results of this work will be used to benchmark corrosion simulation models.

Corrosion resistance of weight reduced AlxCrFeMoV high entropy alloys

High entropy alloys with superior hardness and corrosion resistance have proved themselves excellent coating materials. In this study, a pitting corrosion resistance analysis of AlxCrFeMoV alloys (with x = 0, 0.2, 0.6, 1), with outstanding mechanical features, has been conducted. The study was motivated by their exceedingly high pitting resistant equivalent number (PREN) values, in the range of 80–100. Powder metallurgy techniques, including mechanical alloying and spark plasma sintering, were applied to fabricate the designed alloys. To examine the pitting behavior of the alloys, the potentiodynamic and cyclic polarization analysis were performed in 3.5 wt% NaCl solution at 25 °C. The electrochemical impedance spectroscopy has been used to study variations in the surface characteristics of specimens in a saline environment. Also, the comparative chemistry of the passive layers formed in the primary and secondary passivation regions was evaluated by conducting X-ray photoelectron spectroscopy. The examined systems exhibited an exceptionally high pitting resistance, which was attributed to being predominantly caused by the high concentration of PREN elements in the alloys. Contrary to previously reported aluminum (Al) containing high entropy alloys, the addition of Al did not have an adverse effect on the pitting behavior of the current systems. This was due to the absence of Al-rich phases.

Effect of annealing temperature on pitting behavior and microstructure evolution of hyper‐duplex stainless steel 2707

AbstractHyper‐duplex stainless steel (HDSS) 2707 is a competitive material for application in extremely caustic environments. In this study, different annealing temperatures ranging from 1020°C to 1200°C were examined by electrochemical tests and microstructure analysis. The microstructure characterization indicated that precipitations were detected when the annealing temperature was below 1050°C and a relatively balanced austenite–ferrite phase structure was obtained at 1100°C. Through electrochemical measurements in NaBr solution, it was revealed that with the increase of temperature the pitting resistance of HDSS 2707 first rose then declined, peaking at 1100°C. The highest critical pitting temperature was about 67°C. In addition, the pitting position shifted from austenite phase to austenite–ferrite boundary and finally to ferrite interior with the annealing temperature increasing, which was in agreement with the pitting resistance equivalent values (PREN) of the two phases.

Effect of Annealing Temperature on Mechanical Behavior, Pitting Resistance and Grain Boundary Character of a 2304 Lean Duplex Stainless Steel

The effect of the annealing temperature on mechanical behavior, pitting resistance, and grain boundary character of 2304 lean duplex stainless steel was studied. For this purpose, 4 mm thick hot-rolled sheets were cold-rolled up to a thickness of 1 mm, followed by isochronal annealing from 900 °C to 1100 °C for 180 seconds. Microstructural and CSL boundary analysis were carried out by electron backscatter diffraction technique. The SIM formation was examined by transmission electron microscopy and the phase distribution was quantified by X-ray diffraction. Mechanical properties were evaluated based on microhardness measurements and tensile tests, and the electrochemical analyses were performed by potentiodynamic polarization studies. The results revealed a Nishiyama–Wasserman relationship between α′-martensite laths and the metastable austenite after cold rolling. Increasing temperature enhanced the softening and ductility but decreased yield and tensile strengths of specimens. The deformation-induced martensitic transformation took place less actively and the strain-hardening rate decreased at higher temperatures. The improvement in ductility was related to the increasing fraction of $$ \sum 3 $$ boundaries in the austenite, whereas the strength worsening was associated with the increasing fraction of the $$ \sum {13b} $$ boundaries in the ferrite as temperature increased. The nucleation of metastable pits changed from austenite to the ferrite phase and the pitting potential shifted to nobler values with increasing annealing temperature. The increasing pitting resistance of austenite was associated with the increase in the fraction of $$ \sum 3 $$ boundaries, while the decreasing pitting resistance of ferrite was related to the increased fraction of the $$ \sum {13b} $$ boundaries at higher annealing temperatures.

Localized corrosion behavior of a single-phase non-equimolar high entropy alloy

In previous work, a design approach combining computational modeling and empirical knowledge has been reported to establish a more efficient paradigm for developing future corrosion resistant alloys. Using this approach, a single-phase non-equimolar high entropy alloy (HEA) was successfully designed and synthesized. In this work, a detailed experimental investigation of the localized corrosion behavior of this alloy is presented. The HEA was found to possess superior intrinsic pitting resistance and exhibit strong passivity, even in 6 M HCl. The ability of this HEA to initiate and propagate a pit has been studied. The pitting resistance was shown to result from the formation of a passive film with exceedingly strong resistance to breakdown and from a high resistance to pit propagation. Pitting was found to be significantly inhibited because of the extremely strong passivity, even in solutions with lower pH and higher chloride concentration than found in a typical local pit environment. The outstanding properties of the HEA validate the approach used for designing corrosion-resistant HEAs.

Effect of Pulse Frequency on Microstructural and Corrosion Properties of Inconel 718 Gas Tungsten Arc Weldments

A study has been carried out to understand the effect of pulse frequencies on the formation of laves phase, the microstructural and corrosion properties of Inconel 718. Bead on welds was made by using gas tungsten arc welding (GTAW) in pulsed mode at different frequencies such as 2, 4, 6, 8 and 10 Hz. Varying frequencies exhibit significant changes in weld surface ripples. Microstructural analysis revealed that the welds at 2, 4 and 6 Hz showed both columnar and equiaxed dendrite structure, while at 8 and 10 Hz, the welds predominantly had equiaxed dendrites. Scanning electron microscopy results showed a reduction in continuous laves phase with the increase in pulsing frequency. Corrosion studies confirmed that the pitting resistance was increased at a higher frequency due to the reduction in laves phase in welds.

Influence of Heat Input and Cold Wire Feeding Rate on Pitting Corrosion Resistance of Submerged Arc Welding Duplex Stainless Steel Welds

Welding thermal cycles may severely impair duplex stainless steel (DSS) performance, especially local pitting resistance and toughness. The restricted welding energy between 0.5 and 2.5 kJ mm−1 represents a limiting factor for productivity increase in DSS welding, and the addition of cold wire is an interesting alternative to increase the welding deposition rate without adding extra heat. The aim of this work is to evaluate the influence of the cold wire feeding rate (CW) and heat input (HI) on pitting corrosion behavior of DSS UNS S32304 bead-on-plate welds obtained by submerged arc welding (SAW). Cyclic potentiodynamic polarization was carried out in transverse weld sections using 1 mol L−1 NaCl solution at room temperature. Most pitting corrosion spots were located on the heat-affected zone (HAZ), and the pitting potentials were lower than the base metal due to higher ferrite fractions and the presence of chromium nitrides. Considering the same CW, the HI increasing reduced Epit for 1.6, 1.9, 2.2 kJ mm−1, but increased Epit for 2.7 kJ mm−1, due to a balance between the HAZ width and the austenite fraction.

Additively manufactured 316L stainless steel with improved corrosion resistance and biological response for biomedical applications

Enhancing the corrosion resistance and improving the biological response to 316 L stainless steel is a long-standing and active area of biomedical research. Here, we analyzed the structure and corrosion tendency of selective laser melted-additively manufactured (AM) 316 L stainless steel (AM 316L SS) and its wrought counterpart. SEM analysis showed a fine (500–800 nm) interconnected sub-granular structure for the AM 316L SS, but a polygonal coarse-grained structure for the wrought sample. Relative to the wrought sample, the AM 316L SS also exhibited a higher charge transfer resistance and higher breakdown potential (˜1000 mV vs. SCE) when tested in biological electrolytes, which included human serum, PBS, and 0.9 M NaCl. A higher pitting resistance (extended passive region) and improved stability of the AM 316L SS was attributed to its dense structure of oxide film and refined microstructure. Finally, material compatibility with pre-osteoblasts was analyzed. Large cytoplasmic extension of osteoblast cells and retention of stiller morphology was observed when cells were cultured on the AM 316L SS as compared to its wrought counterpart, suggesting that the AM 316L SS was a better substrate for cell spreading and differentiation. The differentiation of cultured cells was further validated by western blot for Runx2. Runx2, an anti–proliferative marker indicative of differentiation, was equivalent in cells cultured on either samples, but overall more cells were present on the AM 316L SS. Given its higher corrosion resistance and ability to support osteoblast adherence, spreading and differentiation, the AM 316L SS has potential for use in the biomedical industry.

Spindle speed in friction surfacing of 316L stainless steel – How it affects the microstructure, hardness and pitting corrosion resistance

Using friction surfacing (FS), stainless steel 316L coatings were successfully fabricated on 304 substrates. The spindle speed employed in FS was found to have a more significant effect on the microstructure of the coating surface than that in the cross-section. Compared with the as-received 316L consumable rod, hardness improvement was observed in FSed coatings owing to dynamic recrystallization (DRX) during FS. Moreover, the pitting corrosion resistance of the FSed coatings was enhanced by the severe plastic deformation (SPD), which fragmented the micro-sized MnS inclusions in the consumable rod into inconspicuous size after FS. From the immersion test, pits were gathered in {111} grains of the coatings, and the inferior pitting resistance of the {111} grains could be attributed to their lower stacking fault energy. They sustained considerable elastic strain during FS, and generated a higher residual tensile stress that led to pitting. For the coatings fabricated at a moderate spindle speed (1500 rpm), discontinuous DRX became dominant and the recrystallized random orientated grains weakened the {111} texture, resulting in the highest pitting resistance. However, the pitting corrosion resistance improvement induced by the crystallographic effect of different spindle speeds was less prominent comparing with that caused by MnS inclusion fragmentation. Moreover, the advancing side of the FSed coatings was plastically deformed severely, leading to a stronger {111} texture than in other places, which restricted the pitting corrosion resistance enhancement of entire FSed coating.

Pitting Corrosion of Thermally Aged Duplex Stainless Steels at Different Temperature for Long Time

The pitting corrosion of three duplex steels (DSS), SAF2205, SAF2507, Z3CN20.09M thermally aged at 350 - 500 ℃ for 5500 h was investigated by the means of electrochemical techniques. The pitting potential (Ep) of thermally aged Z3CN20.09M specimens decreased with increasing of ageing temperature, however, the Ep of SAF2205 and SAF2507 thermally aged specimens decreased first and reached the lowest value at 450 ℃ and then increased slightly. The electrochemical impedance spectroscopy results are coincident with the potentiodynamic polarisation testing results. The variation in the charge transfer resistance of specimens coincided with the Ep values. There is little influence of low temperature (below 350 ℃) on resistance to pitting of SAF2205 and SAF2507 DSS. But, the pitting resistance of them degrades drastically ageing at higher temperature above 450 ℃. The deterioration in pitting resistance of thermally aged DSS specimens mainly attributes to the precipitation of Cr-rich α′ phases which affected by temperature markedly. At the range of 350 -500 ℃, the temperature the higher, the precipitation of Cr-rich α′ phases the more. The formation of G phases and the healing process during the long thermal ageing at 500 ℃ is the other reasons for the change in pitting resistance.

Optimization of the composition of austenitic stainless nitrogen-containing steels with high corrosion and mechanical properties

The study investigated 16 grades of austenitic stainless steels (ASS) with different chemical composition, including nitrogen. Metallographic and electrochemical studies of pitting corrosion in a solution of 3.5% NaCl (GOST 9.912) were carried out. The optimum ratios of carbon and nitrogen concentrations in ASS are determined, which allow obtaining high resistance to pitting corrosion and high strength. Equation of the dependence of break down potential Eb and strength (Rp0.2 and Rm) on the chemical composition of the steels with nitrogen were proposed. The effect of heat treatment and severe plastic deformation on the pitting resistance, mechanical and paramagnetic properties of the HNS has been studied. It was shown that during SPD, the HNS strength increased by about 3 times, while the fracture was not brittle and occurred by the quasi-cleavage mechanism. Although the potential of Eb decreased, it remained higher than that of steel 09Cr18Ni10Ti. The HNS of the investigated composition also showed high resistance to stress corrosion cracking in a quenched and aged at 500 zC states, and did not show embrittlement in a corrosive environment even after SPD.

Effects of Heat Treatments on the Corrosion Behavior of 13Cr Stainless Steels in Chloride Solutions Containing Carbon Dioxide

Various electrochemical measurements were adopted to explore the effects of heat treatments on the corrosion resistance of 13Cr martensitic stainless steels in Cl– solutions containing carbon dioxide. Phase contents and lattice strains were measured by Matlab image processing and X-ray diffraction, respectively. The compositions of passive film were tested by X-ray photoelectron spectroscopy. The results showed that the enhancement of austenitized temperature can improve the pitting resistance, whereas uniform corrosion resistance can be injured by the formation of retained austenite. The quenched specimen exhibited enhanced passivation stability in long-term immersion tests. Tempering at 280°C as the optimum process can guarantee 13Cr stainless steel a refined microstructure with reasonable internal stress and easy to obtain an intact protective passive film, which can serviced in complicated CO2 and Cl– corrosion environment.