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Sulfide stress corrosion cracking (SSCC) in crude oil field environment including hydrogen sulfide (H₂S) has been recognized as a materials failure mechanism. Welding residual stress generation and metallurgical change by fusion welding process increase the cracking driving force and reduce the resistance of brittle fracture as well as environmental fracture. On the base of this understanding, firstly, we analyzed welding residual stresses of welded ASTM A106 Gr B steel pipe using in the petrochemical plant. And next, SSCC tests were conducted to assess SSCC resistance of the weld with smooth specimens. From the result, influence of temperature on corrosion rate was sensitive in order of HAZ, base metal and weld metal. Therefore, the most sensitive region in the weld is HAZ, and its corrosion rate increases with the temperature of corrosion environment increase. And failure positions of the most cases among failed specimens were at HAZ of the weld. Low limit (σ_SSCC) of A106 Gr B steel pipe was assessed as 0.6 σ_y (7271.6N)

AgCuZnSn filler metals were prepared from the BAg34CuZnSn filler metal by a combinative process of brush plating and thermal diffusion, and the prepared filler metals were applied to the induction brazing of the 316LN stainless steel. The corrosion behaviors of the brazed joints was evaluated based on local corrosion analyses, where the morphology of the joints was analyzed by scanning electron microscopy (SEM) after immersion in a 3.5 wt.% NaCl aqueous solution and electrolytic etching in a 10 vol.% oxalic acid solution. The microstructure of the brazed joints with the Sn-plated filler mainly consisted of the Ag phase, Cu phase, CuZn phase, Cu₅Zn₈ phase, Cu${}_{41}$Sn${}_{11}$ phase and Ag₃Sn phase. The local corrosion analysis results indicated that galvanic corrosion occurred near the interface between the stainless steel base metal and the brazing seam. With increasing local corrosion time, the corrosion rates of both the brazing seam and the base metal first exhibited an increasing trend, followed by a decreasing trend, and the corrosion rate of the brazing seam was slightly greater than that of the base metal. The corrosion behaviors analysis indicated that the corrosion resistance of the brazing seam was reduced, and concave defects emerged after electrolytic etching for 90 s.

Surface composites are developed on Mg RZ 5 alloy by friction stir processing. During FSP, hard reinforcements are introduced into the matrix of RZ 5 alloy and dispersed uniformly by mechanical stirring action. The reinforcements dispersed were boron carbide, carbon nanotubes (multi-walled) and an 80:20 mixture of zirconia and alumina particles. Dynamic recrystallization and grain boundary pinning action by reinforcement particles resulted in the generation of fine-grained surface composites. Corrosion characteristics of the base material and the surface composites are studied by potentiodynamic polarization technique. The corrosion rates estimated for the surface composites are found to be far lesser than the base material while their polarization resistances were higher than the base material. Among all surface composites, B₄C particle reinforced surface composites exhibited the lowest corrosion rate of $\sim$15 mpy. Reduction in the corrosion rate of the surface composites is influenced by fine-grained microstructure and presence of harder reinforcement particles.

In this work, the surface properties of Mg–Al–Zn (AZ91D) alloy such as surface morphology, hardness and electrochemical corrosion were studied after copper ions (Cu${}^{+})$ irradiation at different energies (0.8, 1.5, 2.5 and 3.5MeV) while keeping the ion dose constant at $5\times 10^{14}$ ions/cm². The morphological features of irradiated samples showed defects composed of ejected material from the alloy surface that became more significant at 3.5MeV. The Vickers hardness was increased with increase of the Cu${}^{+}$ energy. The electrochemical testing of the samples was conducted in a Ringer Lactate solution. The potentiodynamic polarization results revealed anomalous changes in the corrosion rate of the Mg alloy with increase of the Cu${}^{+}$ energy. The corrosion rate was considerably decreased with increase of the Cu${}^{+}$ energy to 3.5MeV. These changes were associated with the surface defects and passive film formation on the alloy surface.

Measuring the corrosion rate of a corroding metal is of interest in many situations including monitoring industrial processes and fundamental research in laboratories. The corrosion rate of a metal can be measured electrochemically by determining its polarization resistance, which is inversely proportional to the corrosion rate. What is introduced in this letter is a novel technique for extracting polarization resistance from electrochemical noise (EN) data. An advantage of this approach is that very short time records, of the order of a few seconds, can be assessed to see if they reveal a polarization resistance. The theoretical framework for this approach is based on a time-domain analysis of an electrical circuit model of an EN experimental arrangement. The analysis indicates that polarization resistance can be interpreted only if one electrode, not both electrodes, is predomi-nately generating electrochemical transients during a given time record. An algorithm for extracting polarization resistance from EN measurements is described and examples of its implementation on EN data support the features of the theoretical framework.

This study focuses on the electroless deposition of Ni–P alloy over a copper substrate to minimize the corrosion rate of the substrate. Central Composite Design (CCD) has been performed using Design-Expert software for minimizing the corrosion rate of the coating. Along with that, CCD is also utilized to analyze the influence of various process parameters viz. concentration of Nickel Sulphate, the concentration of Sodium Hypophosphite and bath temperature. Potentiodynamic test has been employed to evaluate the corrosion rate of each of the coated substrates. In order to minimize the corrosion rate, optimization has been performed using particle swarm optimization (PSO). 21.59g/L of Nickel Sulphate, 26. 72g/L of Sodium Hypophosphite and 93.41°C as the bath temperature were the optimum conditions for the deposition of coating in order to achieve a corrosion rate value of 0.862mm/Yas obtained from the model analysis results. Further, Analysis of Variance (ANOVA) was implemented which corroborated that the parameter Nickel Sulphate along with the interaction between Sodium Hypophosphite and bath temperature were the significant ones in determining the corrosion rate of the coating deposited in optimized condition. Optical Microscopy, Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray analysis (EDX) were conducted to study the surface morphology and the elemental composition of the coated substrate respectively.

Galvanic corrosion will happen when the top coating of aluminum alloy joint-structures which abound in the aircraft damages. The corrosion type of aircraft materials is atmospheric corrosion that is the electrochemical corrosion under the thin layer electrolyte. The electrochemical properties of the materials covered with the 0.5mm thick film by self-made electrochemical measurement device have been researched in this paper. The potential distribution and corrosion rate of lap joints after the coating damaged have been calculated by BEASY. The simulation results show that the closer to the bolts, the greater the current density of aluminum alloy, the faster the corrosion rate; the corrosion rate is closely related to the coating damage area, the smaller the damage area, the bigger the corrosion rate in the region of coating damage.