Corrosion Behavior Of Welded Joints Research Articles

CO2 Corrosion of X80 Steel under High Shear Flow Fields

Corrosion failure accidents owing to flow erosion and pipeline corrosion frequently occur during transportation. In this study, a high wall shear stress (WSS) experimental setup was established to conduct the online electrochemical corrosion test. The corrosion behavior of welded joints in NACE solution was studied by electrochemical experimental methods such as electrochemical impedance spectroscopy (EIS) and wire harness microelectrode (WBE). The results show that different areas of the welded joint show different corrosion phenomena in NACE solution. The weld metal (WM) has the significantly better corrosion resistance, while the base metal (BM) and heat-affected zone (HAZ) have worst corrosion resistance than WM. The current of the WM surface was cathodic current, while the current of the BM and HAZ surface were anode currents.

Microstructure and corrosion behavior of welded joint between 2507 super duplex stainless steel and E690 low alloy steel

Microstructure and corrosion behavior of welded joints between super duplex stainless steel 2507 and low alloy steel E690 were characterized herein. The joints are composed of base metal and heat affected zone (HAZ) of the two steels, weld metal, and dilution zone at the interface between weld metal and HAZ of E690 steel. Concentration gradients of Fe, Ni, Cr, and Mo exist between fusion boundary and Type-II boundary, and martensite band with a high hardness is formed. The changes of microstructure, element diffusion in different regions, and local acidification in E690 HAZ lead to heterogeneous corrosion attacks on the welded joints in artificial seawater. After long-term exposure, a corrosion groove is generated at the HAZ of E690 adjacent to the interface, where high stress corrosion cracking vulnerability is expected.

Investigation of mechanical and corrosion behavior of laser hybrid weld joint of 2205 duplex stainless steel

PurposeDuplex stainless steel is composed of equal amounts of austenite and ferrite, which has excellent corrosion resistance and strength. However, after the metal was welded, the ratio of austenite and ferrite in the joint is unbalanced, and secondary phase precipitates are produced, which is also an important cause of pitting corrosion in the joint.Design/methodology/approachThis paper aims to study the mechanical and corrosion behavior of welded joints, by adjusting the welding parameters of laser hybrid welding, dual heat sources are used to weld 2205 duplex stainless steel. The two-phase content of different parts of the welded joint is measured to study the influence of the ratio of the two-phase on the mechanical and corrosion properties of the joint.FindingsThe ratio of austenite and ferrite in different welded joints has an obvious difference, and from top to bottom, the austenite content decreased gradually, and the ferrite content increased gradually. The harmful phases are precipitated in the middle and lower part of the joint. The strength of welded joints is slightly lower than that of base metal. At the same time, the fracture analysis shows that some ferrite phases are affected by the precipitate in the grain and produce quasi-cleavage fracture. The corrosion results show that the corrosion resistance of the welded joints is lower than that of the base metal, and the concentration of chloride ions affects the corrosion resistance.Originality/valueIn this paper, the authors use the influence of different welding processes on the two-phase ratio of the joint to further study the influence of the microstructure on the corrosion resistance and mechanical properties of the weld.

Global and Local Corrosion of Welded Joints of High-Strength Low-Alloy Automotive Steel

Global and local corrosion techniques were used to study the corrosion behavior of weld joints of a high-strength low-alloy steel (LNE500) typically used in the automotive industry in Brazil. The welded joints were prepared by gas metal arc welding. Two welding transfer modes were used to obtain different heat inputs: pulsed (PUL) and cold metal transfer (CMT). Local and global corrosion analysis techniques presented complementary information. While the local in situ analysis (scanning vibrating electrode technique) revealed the weld metal (WM) as the region where corrosion started, conventional electrochemical techniques (potentiodynamic polarization [PP] and electrochemical impedance spectroscopy [EIS]) revealed a higher corrosion rate in the coarse-grained heat affected zone, which was preferentially corroded. A superior corrosion resistance of the WM obtained using CMT over the PUL transfer mode was revealed by EIS and PP. In addition, the results from CMT and PUL samples show that the austenite grain size affects the propagation of the corrosion process. The results are discussed based on microstructural and compositional aspects of the different regions that characterize the welded joints.

Corrosion behavior of the weld joint of X80 pipeline steel in an acidic red soil

In this paper, the corrosion behavior of X80 pipeline steel weld joints in an acidic red soil solution was studied. The results show that uniform corrosion occurs on the entire surface of the weld joint after 840 h immersion. The corrosion degree of heat affected zone (HAZ) is more serious than that of base metal (BM) and weld zone (WZ). The corrosion rate of HAZ specimen is always higher than those of WZ and BM specimens throughout the separated immersion. The accelerating corrosion of HAZ may come from its microstructure change, its corrosion sensitivity and the deterioration of mechanical performance of corrosion product on it.

Mechanical and Corrosion Behavior of Pure Aluminium Added Friction Stir Weld Joint of Aluminium Alloy

Friction stir welding (FSW) of AA2014 aluminium alloy was performed by sandwiching pure aluminium (Al) in the form of strip between the abutting surfaces. Mechanical and corrosion behavior of weld joint with and without pure aluminium addition was compared. Friction stir welding was carried out at rotational speed of 931 rpm and traverse speed of 41 mm/min. Pure aluminium strip of 1 mm thickness was used for incorporating Al in weld nugget zone. Microstructure analysis was carried out using optical microscope and FESEM with energy dispersive spectroscopy (EDS). Microhardness and tensile testing were performed on the weld joints. Corrosion behavior was investigated using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (Tafel) test. FESEM analysis was performed before and after corrosion test. Traces of pure aluminium strip were observed in the microstructure. The incorporated strip was found not to be uniformly distributed in the nugget zone. Pure aluminium addition reduced the extent of formation of the second phase particle in the nugget zone as compared to the normal FSW joint i.e. without Al addition. This metallurgical homogeneity resulted in better corrosion resistance of the Al added weld joint than the normal FSW joint.

Corrosion Behavior of Welded Joints of X70 Pipeline Steel Produced by High-frequency Welding

Corrosion behavior of welded joints of steel pipe category X70 produced by high-frequency welding, in different conditions, in which it is possible to initiate stress-corrosion cracking, hydrogen or sulfide cracking, was investigated. According to the results of electrochemical researches, the kinetic parameters of the cathode and anode processes on the surface of the welded joint of pipe in the investigated solutions are determined. Corrosion resistance of the welded joint HFW-pipe is similar to corrosion resistance of the base metal.

Twin-Wire Pulsed Tandem Gas Metal Arc Welding of API X80 Steel Linepipe

Twin-Wire Pulsed Tandem Gas Metal Arc Welding process with high welding production efficiency was used to join the girth weld seam of API X80 steel linepipe of 18.4 mm wall thickness and 1422 mm diameter. The macrostructure, microstructure, hardness, and electrochemical corrosion behavior of welded joints were studied. Effects of temperature and Cl− concentration on the corrosion behavior of base metal and weld metal were investigated. Results show that the welded joint has good morphology, mechanical properties, and corrosion resistance. The corrosion resistance of both the base metal and the weld metal decreases with increasing temperature or Cl− concentration. In the solution with high Cl− concentration, the base metal and weld metal are more susceptible to pitting. The corrosion resistance of the weld metal is slightly lower than that of the base metal.

Investigation of Corrosion Behavior of Welded Joint of X70 Pipeline Steel for Deep Sea

Investigation of Corrosion Behavior of Welded Joint of X70 Pipeline Steel for Deep Sea

Effects of Friction Stir Welding on Corrosion Behaviors of AA2024-T4 Aluminum Alloy

In this work, the corrosion behavior of welded joints of AA2024-T4 Al alloy produced by friction stir welding process has been investigated. Tests were performed in an aerated 3.5% NaCl aqueous solution with pH = 7 at 20±2°C. Corrosion rate and corrosion morphology of weld regions were evaluated and compared to those of the parent metal. The microstructure of weld nugget, thermomechanical affected zone, heated affected zone, and parent metal were analyzed using scanning electron microscopy and energy dispersive spectroscopy. It was observed that corrosion initiated at FSW related spots and the sizes of local corrosion increased with time.

Joint Characteristics and Corrosion Properties of Bypass-Current Double-Sided Arc-Welded Aluminum 6061 Alloy with Al–Si Filler Metal

Sheets of aluminum 6061 alloy were welded using bypass-current double-sided arc welding with Al–Si filler wire to investigate the effect of Al–Si intermetallic compounds on the microstructure, microhardness and corrosion behavior of weld joint. Experimental results indicated that the Al4.5FeSi phase in the topside of the weld joint was finer than that in the backside and newly formed phase of Al0.5Fe3Si0.5 was observed in the backside. The formation of reinforcing phases of Al–Fe–Si in the weld improved the microhardness of the weld by about 18%. The corrosion resistance of the weld zone was greater than that of the base metal, while the corrosion current displayed opposite, and the corrosion resistance of the weld region was better than that of the base metal.

Metallurgical investigations and corrosion behavior of failed weld joint in AISI 1518 low carbon steel pipeline

In this paper, failure analysis was carried out based on the available documents, metallographic studies and corrosion behavior of the welded joint pipe sample made of AISI 1518 low carbon steel. Nondestructive evaluations including penetration test (PT) and radiographic test (RT) were performed on the as-received pipeline and results indicated the presence of micro- and macro-cracks. Optical microscopic images and scanning electron microscopy (SEM) micrographs revealed various microstructures in the base metal (BM), heat affected zone (HAZ) and weld metal (WM). The microstructural variations may result in galvanic feature and lead to failure and rupture of the weld joint during the service. Microhardness measurements showed that hardness value was about 260 HV in the WM, while it declined in the HAZ and BM. Qualitative chemical analyses such as X-ray diffraction pattern (XRD) and SEM equipped with energy dispersive spectroscopy (EDS) confirmed the presence of corrosive media during weld joint rupture. Additionally, SEM and optical investigations indicated that micro-cracks were formed in HAZ due to residual stress as a consequence of improper welding condition. Surface fracture studies showed that the crack initiation, crack growth and finally crack propagation took place in the WM/HAZ interface. Electrochemical studies were conducted on the BM, HAZ and WM to investigate corrosion behavior of the failed joint sample. Finally, a proper corrosion mechanism is proposed based on the failure analyses and electrochemical studies.

Corrosion of welded joints of bimetallic composite tube in simulated offshore gas field environment

Purpose – The purpose of this investigation was to research the corrosion behavior of welded joints of bimetallic composite tube (X65/316L) welded with Inconel 625 in simulated sea water and in simulated production water, respectively. Design/methodology/approach – The different electrochemical corrosion and galvanic corrosion behaviors of different welded zones were identified using the dynamic potential scan method and galvanic corrosion technique. Findings – The heat-affected zone (HAZ) of welded joints was the most critical zone for corrosion. The closer to the welding line, more severe was the corrosion that was evident in the HAZ at room temperature. In welded joints of X65 tested in simulated seawater, tremendous corrosion occurred in the HAZ, followed by the base metal, and finally the welding line. However, there were few differences in corrosion of the different zones of welded joints in 316L in simulated production water. In such joints of 316L, corrosion comparatively attacked more easily to the HAZ. In galvanic corrosion tests, tremendous galvanic corrosion was evident on welded joints on X65, but comparatively slight gavanic corrosion appeared at welded joints in 316L. With the increased temperature, galvanic corrosion of welded joints was enhanced. Originality/value – The results can provide reference for reducing the gavalic corrosion of welded bimetallic composite tube metal in the actual operation.

H 2 S浓度和pH值对X65海管钢焊接接头腐蚀行为的影响

With an autoclave the environment of submarine gathering system was simulated, then in which the influence of concentration of H2S and pH value on the corrosion behavior of weld joints of X65 pipeline steel was investigated by electrochemical techniques, immersion test, SEM and XRD analysis technique. The results show that the free corrosion potential of different portion of the X65 pipeline steel weld joint exhibited a tendency of decrease, but the corrosion density of increase, corresponding to the following order as: the weld seam, the heat affected zone and the base material. The average corrosion rate of the steel weld joints is in the range of 0.1~0.25 mm/a, the increase of the concentration of H2S and the reduction of the pH value can both lead to the in- crease of corrosion rate. The corrosion mode of weld seam of X65 steel is mainly the uniform cor- rosion in the simulated environment, and the corrosion of weld seam is slighter than that of the heat

Corrosion behavior of welded joints in ozonated acidic solution

The corrosion-electrochemical behavior of welded joints of steels and alloys, used as instrumental for organic synthesis processes in the presence of ozone was investigated. It was determined that welded joints in ozonated media are characterized by the increase in anodic current densities in the whole range of potentials and the shift of Е cor more negatively compared with the base metal that is associated with the decrease in active centers, on which ozone can be reduced. In ozone synthesis conditions, the alloy 06ХН28НДТ can be recommended as a structural material for reactors manufacture. In the ozone oxidation processes, it is necessary to pay attention to welded joints, especially for stainless steels such as 18-10 as wide cathodic loop formation on polarization curves indicates their tendency to intergranular corrosion (IGC). Corrosion can also proceed in dangerous areas of pitting formation and repassivation of steels under the ozone action. Welded joints of ferritic stainless steels 08Х17Т show the tendency to IGC in periodical ozone syntheses that precludes the possibility of using welding sets or requires protection of joint.

Corrosion behavior of welded joints of austenitic 06Kh18G9N5AB steel

The corrosion behavior of homogeneous and heterogeneous (with 12Kh18N10T and St 3 steels) welded joints of 06Kh18G9N5AB steel in boiling chloride and alkali solutions and in NACE solution is investigated. The influence of welding methods and electrodes on the structure and distribution of alloying elements in the areas around the welded joints is demonstrated.