Corrosion behavior of the heat affected zone in a 316 L pipeline weld

On-site investigation, scanning electron microscope, energy dispersive X-ray spectroscopy, and cyclic potentiodynamic polarization test were carried out for failure analysis of the 316 L pipeline in this paper. The visual inspection revealed that the inner wall was covered with severe rust, and obvious misalignment and poor appearance were found in the weld. The energy dispersive X-ray spectroscopy result identified the presence of Cl in the inner wall of the pipeline. Some carbides of Cr and Mo precipitated in the heat affected zone, which partially deteriorated the corrosion resistance. The cyclic potentiodynamic polarization curve proved that the heat affected zone is not only sensitive to pitting corrosion, but also has inferior repassivation ability. Finally, the pitting preferentially occurred in the heat affected zone and gradually developed to leakage.

Effect of anodic dissolution and passivation on X80 steel in NaHCO3 solution

The effects of extreme stray current on the anodic dissolution and passivation of X80 steel in NaHCO3 solution were investigated using measurements of polarization curves and EIS, AFM and SEM techniques. Under the interference of anodic current (i = 0~200 A/m2), main constituents of corrosion products of X80 steel were FeO(OH) and Fe3O4. A double-layer film formed at i = 100 A/m2, in which FeOOH was in outer and Fe3O4 lied in inner. The formation mechanism of Fe3O4 was confirmed and described by the electrochemical reaction in various regions on anodic potentiodynamic polarization curve.

Synthesis, characterization and corrosion inhibition behavior of 2-aminofluorene bis-Schiff bases in circulating cooling water

Two new bis-Schiff bases, namely 2-bromoisophthalaldehyde-2-aminofluorene (M1) and glutaraldehyde 2-aminofluorene (M2) were synthesized and were characterized, the potentiodynamic polarization curve confirmed that they were anode type inhibitors.

INFLUENCE OF SURFACE ROUGHNESS OF SUBSTRATE ON THE PROPERTIES OF Ni–Co–Fe ELECTRODEPOSITION COATING ON COPPER

Effects of copper surface roughness [Formula: see text] on the properties of Ni–Co–Fe alloy coatings were studied by the measurement of coating roughness, thickness, hardness, substrate/coating bonding force and the potentiodynamic polarization curve. Results showed that at the current density of 4[Formula: see text]A/dm2, the coating roughness increased with the increase of the value of substrate [Formula: see text] in the range 0.1–1.1[Formula: see text][Formula: see text]m. The coating thickness and hardness increased with the decrease of substrate [Formula: see text]. When substrate [Formula: see text] was 0.4[Formula: see text][Formula: see text]m, the substrate/coating bonding force reached the maximum level. When substrate [Formula: see text] was 0.1[Formula: see text][Formula: see text]m, the coating exhibited the best corrosion resistance. The comprehensive properties of the Ni–Co–Fe coatings can be effectively improved by controlling the surface roughness of copper substrate properly.

Pitting Corrosion of Zn Peculiarly Caused by Acetate Anions

The corrosion behaviour of zinc metal was studied in acetate solutions. The potentiodynamic polarization curve in 0.1 M acetate solution displays an anodic peak (A1) owing to the anodic dissolution of zinc followed by a passive layer formation region. Breakdown of the passive film and the initiation of pitting corrosion were observed beyond the pitting potential (

Anode Dissolution Localization of Copper in Water Electrolytes

This article is devoted to investigating a possibility of using electrochemical machining (ECM) technology in manufacturing of printed circuits. Some investigations into the anodic dissolution of copper in aqueous electrolytes under stationary conditions were conducted. The analysis of potentiodynamic polarization curve character allowed revealing both areas of active and passive copper dissolution as well as areas of only active and only passive dissolution. Electrolytes were identified and the concentration of electrolyte solutions where the dissolution process occurs in the above areas was determined. It is shown how to assess a degree of the ECM process localization in electrolytes with surface activation in the treatment area. A simplified function of the localization degree L = i 0 /i without regard for current efficiency was used in the research. Electrolytes with a high degree of electrochemical dissolution localization were revealed. Potential ranges for each of the electrolytes providing a maximum degree of the localization copper dissolution process localization were determined.

Corrosion Performance of AISI-309 Exposed to Molten Salts V2O5-Na2SO4at 700°C Applying EIS andRpElectrochemical Techniques

The corrosion performance of AISI-309 exposed 5 days to molten salts 50 mol% V2O5-50 mol% Na2SO4at 700°C is reported in this paper. Such evaluation was made using three electrochemical techniques: potentiodynamic polarization curve (PC), electrochemical impedance spectroscopy (EIS), and linear polarization resistance (Rp). FromPC, the Tafel slopes,Icorr, andEcorrwere obtained. From Nyquist and Bode plots, it was possible to determine two different stages; the first one showed just one loop, which indicated the initial formation of Cr2O3layer over the metallic surface; after that, the dissolution of Cr2O3formed a porous layer, which became part of the corrosion products; at the same time a NiO layer combined with sulfur was forming, which was suggested as the second stage, represented by two capacitive loops. EIS plots were in agreement with the physical characterization made from SEM and EDS analyses. Fitting of EIS experimental data allowed us to propose two electrical circuits, being in concordance with the corrosion stages. Parameters obtained from the simulation of EIS data are also reported. From the results, it was stated that AISI-309 suffered intergranular corrosion due to the presence of sulfur, which diffused to the metallic surface through a porous Cr2O3layer.

Electrochemical Behavior of Mg in H3PO4 and Phosphating Solution

The electrochemical behavior of pure Mg in H3PO4 acid (0.42 M) and phosphating solution (0.42 M H3PO4+0.34 M ZnO) was investigated through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curve and XRD measurements. The results show that Mg has higher corrosion resistance in the phosphating solution than that in the H3PO4 acid which may be due to the relative protective phosphating film on the surface.