Volume 40, Issue 3

Surface nanocrystallization provides the opportunity to produce gradient-structured metallic materials with improved properties. Several attempts have been made to produce nanostructured stainless steel (SS), along with the study of the resultant corrosion resistance. However, the current knowledge is insufficient to address the corrosion mechanism and the possible ways of enhancing the corrosion resistance after surface treatment. The present work reviews the past significant works on the effect of surface treatment by surface mechanical attrition treatment (SMAT) method as well as its processing parameters on the corrosion properties of SS. The corrosion resistance of nanostructured SS is influenced by the extent of grain refinement, compactness, and homogeneity of the passive film, Cr content, grain boundary structure, composition, and alloying elements. In addition, the resulting corrosion properties can be controlled by choosing the right processing parameters during treatment. Progress on the corrosion behavior of nanostructured steels was summarized and new avenues for further research and developments are proposed.

Galvanic corrosion is a type of localized corrosion that widely exists in all kinds of metal structures and causes severe damage, jeopardising the safety and dependability of equipment. This paper reviews the mechanism of galvanic corrosion and related influencing factors, including the material characteristics and geometric factors of the metal pair and environmental factors. As a unique surface testing technique, wire beam electrode (WBE) is widely used in various corrosion research fields represented by galvanic corrosion. On this basis, the research progress of the WBE technique in the field of galvanic corrosion is mainly reviewed from three perspectives. The experiments also proved that the WBE technique can well characterize the corrosion evolution progression and investigate the polarity reversal mechanisms. Finally, it is pointed out that the urgent scientific problems to be solved in the research of galvanic corrosion include: galvanic corrosion research in a variety of special environments; the mechanism of the galvanic couple reversal caused by the change of corrosion factors; the corrosion behavior of a complex coupling system composed of multiple metal connections; the development of corrosion prediction models.

Numerous attempts have been made to enhance the corrosion inhibition (%IE) of organic compounds. Each method has its own advantages and drawbacks. One of the important methods of enhancing %IE of organic compounds is their chemical functionalization which involves addition of polar functional groups, which enhances %IE due to combined effect of enhanced solubility and the number of adsorption centers. A large number of organic compounds derivatized through covalent and noncovalent functionalization are extensively used as corrosion inhibitors. It is well documented that properly functionalized organic compounds show higher %IE than the parent compounds. Other important factors that usually affect corrosion inhibition performance are transportability rate, immersion time, planarity, strength of electrolyte, and synergism. In the present article effect of these factors has been discussed. A proper understanding of these factors will help corrosion scientists and engineers in designing and synthesis (formulation) of effective corrosion inhibitors for industrial scale applications.

In order to understand the corrosion behavior of high-velocity oxygen-fuel (HVOF) TiAlNb coatings in molten Zn-0.2 wt.% Al, the different kinds of TiAlNb coating were deposited on 316L stainless steel substrate and the corrosion tests in molten zinc were carried out. The coating morphologies, phase composition, and characteristics of HVOF TiAlNb coatings at different stages of immersion time were studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectrometry (EDX). The results indicated that the HVOF sprayed TiAlNb intermetallic compound coatings have excellent corrosion resistance to molten zinc. The corrosion type of the HVOF TiAlNb coatings in molten Zn-0.2 wt.% Al is pitting corrosion and crack corrosion. In the whole corrosion stage of molten Zn-0.2 wt.% Al, the corrosion time has no effect on the phase compositions of the HVOF TiAlNb coatings.

Pitting initiation on 304 stainless steel grades was investigated in alternating temperature pore solutions to simulate pitting on stainless steel rebar in a tropical marine environment. The results suggested that a larger amplitude of alternating temperature heavily doped the passive film, reduced the film’s thickness and increased the (Fe 3+ ox + Fe 3+ hy)/Fe 2+ ox and Cr 3+ hy/Cr 3+ ox ratios in the film. Alternating temperatures more significantly degraded the passive film and intensified the pitting sensitivity on the stainless steel when compared with the average temperatures of the alternating temperature cycles. More pitting initiation sites were observed on the samples that experienced the 22–60 °C and 22–70 °C alternating temperature cycles than their counterparts in 50 °C and 60 °C solutions, respectively.

Ni60 coatings with the CeO 2 mass fractions of 3%, 6%, and 9% were prepared on S355 steel. The microstructure and phases of obtained coatings were analyzed using an ultradepth of field microscope (UDFM) and X–ray diffraction (XRD), respectively. The effects of CeO 2 mass fraction on the immersion corrosion behaviors and electrochemical performances of Ni60–CeO 2 coatings in 5% NaCl solution were investigated. The results show that the immersion corrosion rates of Ni60–3%CeO 2 , –6%CeO 2 and –9%CeO 2 coatings are 37.1, 24.3 and 49.2 μm/year, respectively, in which the immersion corrosion resistance of Ni60–6%CeO 2 coating is the best among the three kinds of coatings. The polarization resistances of Ni60–3%CeO 2 , –6%CeO 2 , and –9%CeO 2 coatings are 169,867, 228,568, and 51,276 Ω⋅cm 2 , respectively, and the corresponding charge transfer resistances are 2.66 × 10 5 , 6.68 × 10 5 , and 6.40 × 10 5  Ω⋅cm 2 , respectively, showing that the Ni60–6%CeO 2 coating presents the best electrochemical corrosion resistance in 5% NaCl solution.

In this work, two new imidazoline derivatives (SMF and SMIF) have been synthesized successfully, and their structure have been confirmed by IR, Raman, and NMR techniques. The corrosion inhibition ability and mechanism in HCl solution were proved by experimental and theoretical methods. The inhibition efficiency of SMIF was 94.69% in weight loss experiment, 95.99% (Tafel), and 95.30% (EIS) in electrochemistry. The corrosion inhibition mechanism is that SMF and SMIF form a stable protective film on the surface of Q235 and hinders charge transfer. EDS, FT-IR, and XPS all proved that SMF and SMIF inhibitors could stably adsorb on Q235 surface and form a protective film. The DFT and MD also proved the corrosion inhibiton mechanism. Experiments and theoretical calculations showed that SMF and SMIF exhibited excellent corrosion inhibition performance in 1 M HCl solution.