Based on bibliometrics and information visualization analysis, the global research status and development trends in the field of corrosion and protection were analyzed. By searching the SCI-E database from 1997 to 2017, 106127 related publications in the field of corrosion and protection were obtained. Quantitative and qualitative analysis of the search was conducted in six aspects: basic growth trends and publication language analysis, publication country analysis, document type and journal contribution analysis, institutions analysis, subject categories analysis, keywords analysis. Through journals analysis, the total output of publications in this field shows a sustained and rapid growth trend. In the field, China is the most productive country, meanwhile, it has the fastest growth rate of publications output. United States has the highest h-index and citations per paper. The Chinese Academy of Sciences is the most productive institution. Corrosion Science and Electrochimica Acta are the most influential journals. English is the most common language. In recent years, research directions in this field have focused on materials science, metallurgy/metallurgical engineering, engineering, chemistry, physics, and electrochemistry. And there are three hot topics in this field: studying the corrosion behavior of aluminum alloy, stainless steel, pipeline steel, nickel-chromium alloy, reinforced concrete and other materials; improving the performance of coatings through some special treatment methods (surface modification, heat treatment, micro-arc oxidation, electrodeposition, plasma electrolysis oxidation, etc.) and constantly discoveing some new materials; investigating film preparation and performance optimization.

Pitting corrosion has been found to be responsible for the nucleation of stress corrosion and corrosion fatigue cracks of stainless steel. Meanwhile, the nucleation and growth of pits are both closely related to the stress state, so that it is much more reliable and practical for the corrosion life prediction of mechanical parts by considering the coupling effect of stress and corrosive environment on the pitting corrosion behavior. In addition, such research contributes for us to understand deeply insight into the pitting mechanism and so that to optimize the manufacture technology of stainless steel. This paper reviews the influence of mechanical stresses on every stage of pitting corrosion, including the uniaxial loading, cyclic loading and residual stress on the pitting behavior of the initiation, growth of metastable pitting, transformation from metastable to stable pitting and growth of stable pitting. The relevant research methods are summarized and the effect of mechanical stresses on each stage of pitting corrosion is also analyzed. This work would also provide discussions and outlook of the unresolved issues.

Microbiologically influenced corrosion (MIC) is one of the most common corrosion types of buried pipelines. Many investigations in field survey and laboratory simulation studies have verified that microorganisms in soil and applied stresses can synergistically participate in and significantly affect the crack initiation and propagation of pipeline steels. This phenomenon was named as “microbiologically assisted cracking (MAC)”. Relevant mechanisms, such as pitting mechanism, hydrogen damage mechanism, have been proposed to illuminate this phenomenon. However, there is still a lack of thermodynamic interpretation of MAC and the dynamic analysis deriving from thermodynamic interpretation. In the paper, the thermodynamic interpretation and the dynamic analysis for sulfate reducing bacteria (SRB) /nitrate-reducing bacteria (NRB) -assisted cracking were proposed based on the mechano-chemical interaction theory, bioenergetics and corrosion electrochemistry. The thermodynamic results showed that under the combined actions of SRB/NRB and external stress, the changes of Gibbs free energy of the corrosion reactions decrease and the releasing energies increase accordingly, revealing the stronger corrosion tendency in thermodynamics. For Fe-based alloys, NRB corrosion and NRB-assisted cracking are the more thermodynamically favorable processes, as compared to SRB corrosion and SRB-assisted cracking, respectively. The dynamic results showed that the corrosion rate and the crack propagation rate increase under the combined actions of applied stresses and microorganisms.

The combined effectiveness of the cathodic protection and epoxy coating for a steel, which is newly developed for offshore platform, as well as the cathodic delamination behavior of the epoxy coating with damages in artificial seawater at room temperature were examined by means of electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), energy dispersive spectrum (EDS) and X-ray diffractometer (XRD). Results indicated that as the potential goes down within the selected range of protection potentials of -750~-1050 mV (vs SEC), the delamination area of the coatings increases. The ordinary protection potential -750 mV (vs SEC) for epoxy coatings is no longer applicable for the damaged coatings, while the cathode potential -1050 mV leads to serious hydrogen evolution in the damaged area, resulting in the integrity destruction of the deposited film there, leading to the seriously interfacial alkalization and therewith, the cathodic delamination area increases. However, the protection potential of -850 or -950 mV can inhibit the corrosion of metal on the damaged site of coating. The deposited film formed under -950 mV on the damaged site is composed of Mg(OH)₂ and CaCO₃ which is of integrity and dense, leading to the best protective effect on the substrate.

Oxidation behavior of the shot-peened and bare Super 304H austenitic stainless steel was investigated in 650 ℃/27 MPa steam for 1000 and 2000 h, by means of scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and optical microscopy (OM). It was observed that the oxidation resistance of the Super 304H steel was effectively improved by shot peening. Furthermore, spallation of oxide scale was only observed on the bare Super 304H steel after oxidation for 2000 h. The improvement of oxidation resistance could be attributed to the fact that the shot peening process produced a surface layer of ultra-fine grains with plenty of grain boundaries, sub-grain boundaries and dislocations, which enhanced the diffusion of Cr to form a layer of high density of Cr-rich oxides on the surface. Therefore, the shot peening processing is an effective approach, which not only improved the oxidation resistance to supercritical steam, but also mitigated the exfoliation of oxide scale formed on Super304H steel.

Cemented carbide is widely used in many fields because of its good properties. However, it is difficult to be processed with traditional machining methods. Electrochemical grinding is a kind of non-traditional method which combines electrochemical machining and mechanical grinding with great processing quality and high removal rate. In this paper, electrochemical corrosion mechanism of YG15 cemented carbide in electrolyte of 3 mol/L NaNO₃ is focused by means of potentiodynamic- and potentiostatic-curve measurements. Results show that the electrochemical corrosion of YG15 cemented carbide in NaNO₃ electrolyte is the result of co-oxidation corrosion of WC and Co. Corrosion phenomena vary a lot under different potentials. Moreover, when the anode potential is high, the dissolution rate of metal Co (which acts as the binder) increases, leading to the decreasing adhesion of the formed corrosion product scale to the substrate, which makes the corrosion product scale is prone to spall off. In addition, the corrosion dissolution of the substrate and the spall off for the corrosion product scale may cause the current oscillations on curves of corrosion current vs time, which leads to serious corrosion and even destruction of the substrate surface. Therefore, the anode potential should not excess 3.5 V_Ag/AgCl so that to avoid the above mentioned harmful event during electrochemical grinding. The composition of the corrosion layer is determined to be tungsten oxides (which is mainly WO₃) by energy dispersive spectroscope and X-ray photoelectron spectroscope. Reasonable voltage parameters could help increase the removal rate of materials a lot in electrochemical grinding.

Nyquist plots and Bode impedance module plots of rebar steel in coral aggregate concrete (CAC) exposed in artificial sea water for different times were assessed by means of electrochemical impedance spectroscopy (EIS). The suitable equivalent electric circuit (EEC) for fitting data of the rebar steel corrosion in CAC was proposed. The conversion relationship between charge transfer resistance (R_ct) and polarization resistance (R_p) was established. The influence of the thickness of concrete cover and the rebar steel types on the corrosion behavior of rebar steel in CAC was discussed. The results show that: the EEC mode for the rebar steel electrode in CAC were R_s(C_cR_c)(Q_dlR_ct) in the passivation stage and R_s(C_cR_c)(Q_dl(R_ctW)) in the corrosion stage respectively. As the thickness of concrete cover increased, the R_ct of rebar steel gradually increased, as did the corrosion resistance. Moreover, the corrosion resistance of different rebar steels decreases as the following sequence: 2205 duplex stainless steel ＞316 stainless steel ＞new organic coated steel ＞zinc-chromium coated steel ＞common steel. Therefore, for CAC structures in actual engineering practice, it was suggest to adopt new organic coated steel, while the thickness of concrete cover should be thicker than 5.5 cm, which could prolong the initial stage of rebar steel corrosion, reduce the corrosion rate and prolong the service life of the CAC structure.

The inhibition effect of soybean meal extract (SME) on the corrosion of Q235 carbon steel in 1 mol/L HCl solution was investigated by weight loss method, potentiodynamic polarization curve measurement, electrochemical impedance spectroscopy and scanning electron microscope. The inhibition efficiency increased and then decreased with the increasing temperature in the range of 25~90 ℃. With a dose of 0.8 g/L SME, the inhibition efficiency was 92% at 40 ℃, and the SME acted as a mixed-type inhibitor. The adsorption of SME on Q235 steel accorded with Langmuir isothermal equation, and including chemical and physical adsorption.

The corrosion resistance of Q345E and Cr-Ni-Cu steels was comparatively assessed by means of potentiodynamic polarization and cyclic immersion corrosion tests in 0.052% (mass fraction) NaHSO₃ solution, which aims to simulate the common SO₂-containing atmosphere. The characteristic of corrosion rust was studied by means of scanning electron microscope (SEM) and X-ray diffraction (XRD). Results show that the open circuit corrosion potential of Q345E and Cr-Ni-Cu steel are -730 and -705 mV, respectively. The rust layers of two steels contain γ-FeO(OH) and α-Fe phase. Some α-FeO(OH) and Fe₃O₄ products generate with increasing of the corrosion time. Compared with Q345E steel, the Cr-Ni-Cu steel has lower corrosion rate due to the formation of a much more compact rust layer containing elements such as Cr, Ni and Cu, which are beneficial to corrosion resistance.