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This book describes the work performed to develop a new test methodology to characterise the susceptibility of stainless steels to crevice corrosion in natural and treated seawaters. It also describes the experimental procedures to perform crevice corrosion testing.

The present study investigated the corrosion behavior and mechanism of B10 copper tubes used for shipboard pipelines through various analytical techniques, including macroscopic inspection, chemical analysis, electrochemical impedance, corrosion product morphology, and physical phase and electron microscopic observation. The research findings revealed that the surface corrosion product film on the B10 copper tube in seawater mainly consists of Cu2O. Furthermore, the corrosion behavior under actual working conditions was attributed to crevice corrosion, non-electric coupling corrosion, and the corrosion mechanism was found to be the result of the combined effect of oxygen concentration difference cell and occlusion cell autocatalytic effect. These observations provide valuable insights into the corrosion performance of B10 copper tubes in seawater, which could potentially aid in improving their durability and reliability in marine applications.

To investigate the tribological performance of a copper alloy engine bearing under oil lubrication, seawater corrosion and dry sliding wear, three different PI/PAI/EP coatings consisting of 1.5 wt% Ce2O3, 2 wt% Ce2O3, 2.5 wt% Ce2O3 were designed, respectively. These designed coatings were prepared on the surface of CuPb22Sn2.5 copper alloy using a liquid spraying process. The tribological properties of these coatings under different working conditions were tested. The results show that the hardness of the coating decreases gradually with the addition of Ce2O3, and the agglomeration of Ce2O3 is the main reason for the decrease of hardness. The wear amount of the coating increases first and then decreases with the increase of Ce2O3 content under dry sliding wear. The wear mechanism is abrasive wear under the condition of seawater. The wear resistance of the coating decreases with the increase of Ce2O3 content. The wear resistance of the coating with 1.5 wt% Ce2O3 is the best under-seawater corrosion. Although Ce2O3 has corrosion resistance, the coating of 2.5 wt% Ce2O3 has the worst wear resistance under seawater conditions due to severe wear caused by agglomeration. Under oil lubrication conditions, the frictional coefficient of the coating is stable. The lubricating oil film has a good lubrication and protection effect.

The seawater corrosion behavior of a plain carbon steel covered with hydrothermally carbonized coating was studied. Hydrothermal carbonization of sugar (sucrose) dissolved in water with a concentration of 10 wt.% at 200 °C for 4 h was carried out to produce a carbonized coating on the steel. The corrosion resistance of the steel with and without the carbonized coating was evaluated by polarization tests in seawater. The Tafel slopes were calculated using polarization data. The corrosion current and the potential of corrosion were determined to examine the effect of the carbonized coating on the corrosion behavior of the steel. In addition, AC impedance measurements on the steel without and with the hydrothermal carbonization coating were performed in a three-electrode cell with a Ag/AgCl reference electrode, platinum counter electrode, and seawater electrolyte. It was found that hydrothermal carbonization of sugar generated a continuous carbon-rich layer on the surface of the steel. This carbon layer is highly corrosion-resistant as shown by the decrease in the corrosion current. It is concluded that the hydrothermally carbonized coating has the nature of passivation films, and it can slow down the corrosion rate of the plain carbon steel in seawater. The impedance of the steel without hydrothermal carbonization coating is very low. With hydrothermal carbonization coating, an increase in the resistance and the capacitive response of the coating/seawater interface was observed.

Mineral admixtures exhibit significant enhancement effects on the seawater corrosion resistance of sulfoaluminate cement (SAC). This study systematically investigates the influence mechanisms of fly ash (FA), silica fume (SF), and slag powder (SP) on the physicochemical properties of SAC-based materials. Experimental results demonstrate that FA effectively enhances the fluidity of fresh SAC paste while mitigating drying shrinkage. Under standard curing conditions, the compressive strength of SAC mortar decreases with increasing FA content, reaching optimal performance at a 5% replacement level. However, in seawater immersion environments, FA undergoes chemical activation induced by seawater ions, leading to a positive correlation between mortar strength and FA content, with the 10% replacement ratio demonstrating maximum efficacy. SF addition reduces workability but significantly suppresses shrinkage deformation. While exhibiting detrimental effects on flexural strength under standard curing (optimal dosage: 7.5%), a 5.0% SF content manifests superior seawater resistance in marine environments. SP incorporation minimally impacts mortar rheology but exacerbates shrinkage behavior, showing limited improvement in both standard-cured compressive strength and seawater corrosion resistance. Orthogonal experimental analysis reveals that SF exerts the most pronounced influence on SAC mortar fluidity. Both standard curing and seawater immersion conditions indicate FA as the dominant factor affecting mechanical strength parameters. The optimal composite formulation, determined through orthogonal combination testing, achieves peak compressive strength with 5% FA, 5% SF, and 5% SP synergistic incorporation.

M2052 (Mn–20Cu–5Ni–2Fe, at.%) alloy is known for its excellent damping and mechanical properties, but its corrosion resistance is lacking. Here, a composite coating was developed by chemically plating a Ni–P amorphous coating followed by electroplating a superhydrophobic nickel (SH Ni) coating. The composite coating exhibits super-hydrophobic properties primarily for two reasons. Firstly, the pinecone-shaped structure on the surface of the Ni–P/SH Ni coating has the ability to trap air, thereby forming an air layer. Secondly, through surface modification with stearic acid molecules, there is a significant reduction in the surface energy of the coating. As a result, the Ni–P/SH Ni coating were effective in reducing the corrosion rate, which can be attributed to the effective filling of the surface pores of the Ni–P coating by the outer Ni film, and the superhydrophobic characteristics of the SH Ni coating. This study provides a new idea for corrosion protection of M2052 alloys in marine environment.

In this study, we investigated the electrochemical corrosion behavior and mechanisms of FeCrNi/WC alloys with varying contents of CTC-S (spherical WC) and CTC-A (angular WC) in a 3.5 wt.% NaCl solution, addressing the corrosion resistance requirements for stainless steel composites in marine environments. The electrochemical test results demonstrate that the corrosion resistance of the alloy initially increases with the CTC-A content, followed by a decrease, which is associated with the formation, stability, and rupture of the passivated film. Nyquist and Bode diagrams for electrochemical impedance spectroscopy confirm that the charge transfer resistance of the passivated film is the primary determinant of the composite’s corrosion performance. A modest increase in CTC-A contributes to the formation of a more heterogeneous second phase, providing a physical barrier and enhancing solid solution strengthening, and thus delaying the cracking and corrosion processes of the passivation film. However, excessive CTC-A content leads to significant dissolution of the alloy’s reinforcement phase and promotes decarburization, resulting in the formation of corrosion pits, craters, and cracks that compromise the passivation film and expose fresh alloy surfaces to further corrosion. When the CTC-A content is 10% and the CTC-S content is 30%, this combination results in minimal degradation in the corrosion performance (0.213 μA·cm2) while balancing the hardness and toughness of the alloy. Additionally, electrochemical evaluations reveal that incorporating angular CTC-A particles at 10 vol% effectively delays the breakdown of the passivation film by mitigating the interfacial galvanic coupling through enhancing the mechanical interlocking at the WC/FeCrNi interface. The CTC-A/CTC-S hybrid system exhibits a remarkable 62% reduction in the pitting propagation rate compared to composites reinforced solely with spherical WC, which is attributed to the preferential dissolution of angular WC protrusions that sacrificially suppress crack initiation at the phase boundaries.

Additive manufacturing opens new possibilities for designing light-weight structures using aluminium alloys. The microstructure of two Al alloys and their corrosion resistance in NaCl and natural seawater environments were investigated. The newly designed Al-Mn-Cr-Zr based alloy showed a higher corrosion resistance than reference AlSi10Mg alloy in both environments in as printed and heat-treated conditions. The corrosion initiated in the Al matrix along the precipitates in the alloys where the Volta potential difference was found the highest. The coarser microstructure and precipitate composition of the new Al-alloy led to the formation of a resistant passive film which extended the passivity region of the Al-Mn-Cr-Zr alloy compared to the AlSi10Mg alloy. The effect of heat treatment could be seen in the microstructure as more precipitates were found in between the melt pool boundaries, which affected the corrosion initiation and slightly the pitting resistance. Overall, this study shows that a newly designed Al-alloy for additive manufacturing has a suitable corrosion resistance for applications in marine environments.

Cemented soils are subjected to a variety of adverse environmental conditions in the marine environment, including corrosive seawater exposure, the dry–wet cycle, and temperature variations. These environmental conditions significantly jeopardize the reliability and durability of foundations built on these types of engineered soil. The addition of nanoparticles to this cement treated soils is offered as an engineering solution for extending their service life. Four different nanomaterials that have been extensively studied in the literature are employed as admixtures in the cemented soil. Appropriate dosages of these nanomaterials are determined based on the data from unconfined compressive strength test (UCS) and the scanning electron microscopy (SEM). Wet–dry cycles are applied on the cement treated soil samples to simulate the tidal rise and fall relevant to the marine environment. Nuclear magnetic resonance tests (NMR) are also performed to complement the SEM study. Incorporating Nano-SiO2 into soft soil cured with cement in marine environment improved the mechanical strength and stiffness of the cement soils. It also decayed the corrosion rate of the cemented soils in ocean, and the improvement in mechanical stability was also quite remarkable. After 60 cycles of seawater exposure, the strength of Nano-SiO2 cement soils increased by 3.4 times that of conventional cemented soils, while the corrosion rate decreased by 85%. The improved durability of Nano-SiO2 cemented soils is a function of their structural filling tropism and distribution tropisms. The improved durability of Nano-SiO2 is a result of the combined effect of particle effect, volcanic ash effect and nucleation effect.

Ni–Co–P alloy coatings were successfully fabricated by jet electrodeposition with varying pulse frequencies and duty cycles in order to prolong the longevity of steel C1045 substrates. The results showed that the microstructures and properties of samples were significantly affected by pulse frequencies and duty cycles. All the samples with varying pulse frequencies and duty cycles exhibited a face-centered cubic (FCC) structure. Additionally, the average grain size of the samples reached 20.6 nm. The microhardness of the coatings was observed to first increase, and then decrease, with a rise in pulse frequencies and duty cycles. The microhardness reached 656.2 HV0.1, and the wear scar width of the coatings reached 414.4 µm at 4 kHz pulse frequency and 80% duty cycle. Additionally, the corrosion current densities (Icorr) of samples reached a minimum value of 0.74 µA·cm−2, the corrosion rates (Rcorr) reached a minimum value of 8.9 µm·year−1, and the charge transfer resistance (Rct) reached a maximum value of 8.36 × 104 Ω·cm−2, which indicated the optimal seawater corrosion resistance of the deposited coatings.