Purpose The purpose of this paper is to examine the performance of cold-sprayed Zn15Al alloy coating whether it is capable of protecting magnesium alloy from corrosion, and to compare it with arc-sprayed Zn15Al alloy coating. Design/methodology/approach In this paper, Zn15Al alloy coating was prepared with CS-6000 cold spraying system and HDX-800 arc-sprayed system. Corrosion behaviors of the two kinds of coatings were examined with potentiodynamic polarization curves methods combined with SEM, EDS, XRD, etc. Findings Corrosion behavior of cold-sprayed Zn15Al alloy coating is superior to arc-sprayed Zn15Al alloy coating. The bonding strength and density of cold-sprayed Zn15Al alloy coating is much higher than that of arc-sprayed Zn15Al alloy coating. The cold-sprayed coating has a dense structure which separate magnesium from corrosion medium completely. The samples behave as Zn15Al instead of AZ91D alloy. The coating has a low probability of pitting corrosion comparing with cold sprayed Al coating through potentiodynamic polarization curve. Practical implications Cold-sprayed Zn15Al coating can be used to improve the anticorrosion performance of magnesium significantly and low down the risk of pitting corrosion of coating. Social implications Cold-sprayed Zn15Al coating is an environmentally friendly anticorrosion method for light alloy, which is also the most effective way among thermal spray, chemical vapor deposition, sol–gel, plating and anodizing or microarc oxidation. Originality/value The present paper used cold spray method to deposit Zn15Al coating, which has an overwhelming performance both in physical and anticorrosion to traditional thermal spray method.

Al B4C composites structure manufactured by sintering method suffers from low strength and decomposition. To solve this problem, cold spray technology was used to manufacture Al B4C composite coating on 5083 aluminium alloy. The results indicate that a high content (30 wt-%) B4C reinforced Al coating can be deposited on aluminium substrate through cold spraying. The microstructure of the coating was characterized using scanning electron microscopy. It was found that the cold spray could deposit good quality aluminium coating with bonding strength ranging from 26.5 to 28.2 MPa. The average porosity for this coating in this case is about 1.5%, and the B4C particles distribute uniformly in the coating. Electrochemical tests revealed that the cold sprayed Al + 30% B4C coating has an inferior corrosion resistance to 5083 aluminium alloy in neutral 3.5 wt-% NaCl solution. Cold spray is a talented technology to manufacture Al B4C Composites coating for neutron absorption application.

Low pressure cold spraying (LPCS) is different from high pressure cold spraying because it is capable of onsite operation with compaction system and flexible spray gun. However, the deposition efficiency is much low for efficient onsite reparation, it is important to know more about the influence of spraying parameters on deposition efficiency of LPCS. To verify the relationship between the spray parameters (temperature, standoff distance, powder feeding rate, and transverse speed) and the deposition efficiency, a DYMET413 commercial LPCS system was used to prepare coating under different parameters. The deposition efficiency increases linearly as the gas temperature increases. The optimal alumina content in powders is about 30%, the optimal distance is 25mm for the powder used in this study. The deposition efficiency of powder increases as the transverse speed of nozzle decreases. It is hard to predict the deposition efficiency by numerical methods since the deposition behavior in a composite powder system is influenced by a number of factors. The interaction between particles, the erosion effect of alumina and under critical velocity particles all can influence the deposition behavior.

Cold spraying is a promising method for rapid prototyping due to its high deposition efficiency and high-quality bonding characteristic. However, many researchers have noticed that holes cannot be replenished and will grow larger and larger once formed, which will significantly decrease the deposition efficiency. No work has yet been done on this problem. In this paper, a computational simulation method was used to investigate the origins of these holes and the reasons for their growth. A thick copper coating was deposited around the pre-drilled, micro-size holes using a cold spraying method on copper substrate to verify the simulation results. The results indicate that the deposition efficiency inside the hole decreases as the hole become deeper and narrower. The repellant force between the particles perpendicular to the impaction direction will lead to porosity if the particles are too close. There is a much lower flattening ratio for successive particles if they are too close at the same location, because the momentum energy contributes to the former particle's deformation. There is a high probability that the above two phenomena, resulting from high powder-feeding rate, will form the original hole, which will grow larger and larger once it is formed. It is very important to control the powder feeding rate, but the upper limit is yet to be determined by further simulation and experimental investigation.

Cold spray can deposit a composite coating simply by spraying mechanically-mixed Al and Zn powders, while no quantitative data has been reported on the anti-corrosion performance of different composite cold-sprayed coatings. In the present work, the finite element method was used to estimate the cathodic protection effect by simulating the potential distribution on a damaged cold-sprayed AlZn coating on Q235 steel. The results indicate that AlZn coating can only provide a limiting cathodic protection for substrate, because it can only polarize a very narrow zone negative to −0.78 V (vs. SCE, saturated calomel electrode). The remaining area of the steel substrate still has a very high residual corrosion rate. Computational methods can be used to predict the corrosion rate of AlZn coating, and the simulation results were validated by the results of a weight loss experiment.

In the present investigation, a Cu/Al2O3 composite antifouling coating was designed on Q235 steel to improve the service life of vessels, components and structures used in marine environments. The base Al2O3 coat was prepared by flame spraying and the antifouling Cu coat was prepared by cold spraying. The Al2O3 layer serves as an insulation layer to separate the copper coating from electrical connection to the steel substrate in case of galvanic corrosion, which also can guarantee the release rate of Cu(.) and Cu(II) ions under cathodic protection conditions. The physical and antifouling performance were examined and the following conclusions were drawn: An excellent Cu/Al2O3 antifouling coating can be deposited on the steel substrate. The typical bond strength is about 10MPa between Cu layer and Al2O3 layer and bond strength between the Al2O3 layer and the substrate was about 20MPa. The antifouling performance, compared to a blank sample (Al2O3 coated steel) indicates that the Cu/Al2O3 antifouling coating can inhibit 85% of biofouling by barnacles, diatoms and mussels.

Parking in the city has been a major problem in modern days. An efficient way to manage the parking lot and to improve the safety of the driver is very important. Traditional parking lots commonly use security camera, ultrasonic sensors or infrared ray sensors to manage the parking lots. However, these systems are not only expensive but time consuming. Therefore, we present a hybrid intelligent parking system, which is able to inform the drivers where is the empty parking space, lend the drivers to easily record where they parking, provide remote monitoring, and offer the parking spot leading service when drivers forget where they parked. In addition, the security guard of the parking lot could provide the functions of remote monitoring, detection and monitoring of parking in the personal sites, and fire detection. This system also employs the micro aerial vehicle (MAV) as mobile monitoring in the indoor environments instead of monitoring by fixed cameras. Through this paper, we demonstrate our system from both driver's view and security guard's view.

Instead of injected by high pressure powder feeder, powders can be drawn into the nozzle by syphonage effect generated by supersonic gas flow in low pressure cold spray. This characteristic makes low pressure cold spray conveniently for on-site operation. However, no data have ever been reported on the relationship between the nozzle structures and the gas flow in the powder feeder pipe. In this paper, a CFD software (STAR CCM+) was used to calculate the gas flow in nozzle of the DYMET 413 commercial low pressure cold spray system. Variation of structures and process parameters based on the commercial system were also investigated. The syphonage effect is strongly influenced by the powder feeding location, the temperature and pressure in prechamber has little effect on syphonage effect in powder feeder pipe. The syphonaged gas will decelerate the gas velocity and low down the gas temperature in nozzle, so it is best to control the mass flow rate of powder feeding gas by selecting the location. One of the disadvantages is that the particles will collide with the nozzle wall which makes the nozzle a short service life.

An area-efficient high-throughput shift-based LDPC decoder architecture is proposed. The specially designed (512, 1,024) parity-check matrix is effective for partial parallel decoding by the min-sum algorithm (MSA). To increase throughput during decoding, two data frames are fed into the decoder to minimize idle time of the check node unit (CNU) and the variable node unit (VNU). Thus, the throughput is increased to almost two-fold. Unlike the conventional architecture, the message storage unit contains shift registers instead of de-multiplexers and registers. Therefore, hardware costs are reduced. Routing congestion and critical path delay are also reduced, which increases energy efficiency. An implementation of the proposed decoder using TSMC 0.18 μm CMOS process achieves a decoding throughput of 1.725 Gbps, at a clock frequency of 56 MHz, a supply voltage of 1.8 V, and a core area of 5.18 mm2. The normalized area is smaller and the throughput per normalized power consumption is higher than those reported using the conventional architectures.

Electrochemical impedance spectroscopy(EIS) was used to study the corrosion behavior of four Al-based alloys commonly used as sacrificial anode for submarine under wet-dry cyclic conditions with various drying periods.The EIS results showed that the failure of the sacrificial anodes was mainly attributed that the coverage effect of corrosion products on the surface of sacrificial anodes,leading to the decrease of the number of active sites on the anode surface.Thus,the further activation of the sacrificial anodes was prevented.After several wet-dry cycles,the severe accumulation of corrosion products on the anode surface resulted in enlargement at the capacitive loops,indicating significant decrease of the active dissolution of the anodes.The performance of the 4 Al-based alloys under wet-dry cyclic environment may be ranked as the following order: Zn-Al-Cd Al-Zn-In-Cd Al-Zn-In-Mg-Ti Al-Zn-In-Mg-Ga-Mn.

Ni-P coating was prepared on the surface of Mn-Al bronze by chemical-plating method.The morphology and composition of Ni-P coating were studied by SEM and EDAX.The effects of cathodic polarization potential on the coating and deposit film were investigated.The compatibility of Ni-P coating with cathodic protection of Mn-Al bronze was discussed.The results showed that the current for the same polarization potential decreased by coating.The main composition of the deposit film was CaCO3.The deposit layer formed more rapidly and finer at more negative potentials.There was no adverse effect of cathodic polarization on Ni-P coating when the protective potential range was from-0.85 V to-1.05 V(CSE).Ni-P coating and cathodic protection of Mn-Al bronze exhibited good compatibility.

Due to its low processing temperature, cold-sprayed coatings tend to exhibit many advantages over traditional thermal sprayed coatings, such as, lower porosity, oxidation and residual stress levels. These characteristics impart the improved anti-corrosion performance of the cold-sprayed coatings. However, it is not known how much these factors influence the corrosion performance of them. In addition, there are few results on the electrochemical behavior difference between cold and thermally sprayed coatings. In this article, as-deposited cold-sprayed copper, aluminum bulk material, arc-sprayed copper and pure copper are tested with electrochemical methods to compare their electrochemical behaviors in natural seawater. The electrochemical methods included the potential-dynamic polarization curve and electrochemical impedance spectrum. The results indicated that there is no significant difference in the corrosion potential between cold-sprayed and bulk copper materials. The potential of cold-sprayed copper is much different from that of the arc-sprayed one. Polarization curves indicated that the corrosion rate is significantly higher for arc-sprayed copper. The electrochemical impedance spectrum shows that there is no difference in electrode interface structure between cold-sprayed and bulk copper materials. Based on these results it is inferred that the higher corrosion rate for arc-sprayed copper was caused by its high porosity level and oxidation degree.

With Zn and Al mixed powders as raw materials, 65%Zn-Al coatings were prepared by cold gas dynamic spray. The microstructures of the cold-sprayed 65%Zn-Al coatings were characterized by SEM and OM. XRD and EDS were used to analyze the co-deposited characteristics of 65%Zn-Al coatings. The results reveal that a densely co-deposited 65%Zn-Al coating with thickness of about 0.7 mm and porosity of 1.7% is obtained. The deposition efficiency of Al particles on the co-deposited coating is obviously higher than that of Zn particles. The bonding among Zn and Al particles mainly attributes to the plastic deformed mechanical embedding effect, and the combination among particles is tight. Those particles at the interface are broken and fined by continuous collision, so they have relative higher micro hardness than Zn or Al bulk metal. The bonding among the particles in the coating is more strength than the bonding of coating to substrate. There is element diffusion phenomenon in the interface between the coating and the substrate, and no solid solution and compound is observed.

The corrosion behaviors of the cold-sprayed Zn-50Al coatings in seawater were characterized by potentiodynamic polarization and electrochemical impedance spectroscopy(EIS)techniques.The X-ray diffraction(XRD)results of corrosion products and scanning electron microscopy(SEM)analysis of corrosion surface were used to comparatively investigate the corrosion properties of Zn/Al coatings,and to study the selfsealing mechanism.The results indicated that the better corrosion resistance of cold-sprayed Zn-50Al coatings compared with Zn coatings due to the better self-sealing effect which effectively prevents further seawater corrosion.It has more appropriate cathodal protection potential than Al coatings and low corrosion rate than Zn coatings.the corrosion rate of the Zn-50Al coatings retained a low level with time.

The corrosion behavior of Q235 steel coated with cold-sprayed aluminum in seawater was examined by electrochemical methods in this work, and the variation of corrosion rate of the aluminum coating was studied by neutral salt spray test. The result indicates that after immersion in seawater the cold-sprayed aluminum coating was covered with a stable corrosion product scale which effectively prevents the coating from further seawater corrosion. The corrosion rate of the aluminum coating declined rapidly with time in neutral salt spray circumstance.

Aluminium alloy sacrificial anodes are often used to protect marine structures from corrosion in seawater due to their high electrochemical properties. However, there exist some cases such as in ship ballast tank, where the anodes are often immersed in seawater when the tank is ballasted and exposed in the atmosphere with the tank empty. This condition affects the performance of the sacrificial anode. In this paper, we study the properties of an Al-Zn-In-Cd alloy anode with cyclic immersion in seawater in the laboratory. It has been found that the performance of the anode decreases with the wet/dry cycles, showing rising working potential positively and reducing electrical capacity as compared with the condition of full immersion. The testing conditions like atmosphere environment, the period of immersion, and the wet/dry ratio also have significant effects on the performance of the anode.

The interaction behavior between aluminum particles in cold spray process is analyzed by numerical simulation method using ANSYS/LS-DYNA and microscopic observation methods. The results indicated that: The repellant force between the particles perpendicular to the impaction direction will lead to porosity if the particles are too close, and properly distance can produce role-ups which will significantly improve the bonding strength. Much lower flatten ratio occurred for succeeding particle if the particles are too close at the same point because the momentum energy convert to the former particle's deformation, which will decrease the dense of the coating. It can be inferred that high powder feeder rate must be avoided because it will lead to many defection for cold spraying coating such as porosity, lower bonding strength.

Pitting resistance of air cold plasma-oxidation 316L stainless steel was evaluated by exposing the specimens into a ferric chloride solution. The results indicate that the pitting resistance of plasma-oxidized specimens improved obviously. Potentiodynamic polarization curves were measured to study its corrosion behavior. The corrosion mechanism was also interpreted by electrochemical impedance spectroscopy (EIS) and Auger electron spectroscopy (AES).The results reveal that the oxide layer formed by the plasma treatment is much thicker than that without treatment and is double-deck structure, which leads to the change of EIS characteristic of sample surface.

In this paper, the in-situ exposure tests of 15 kinds of copper and its alloys were carried out in seawater at Zhanjiang Harbor for 12 months in order to study their anti-fouling abilities and anti-corrosion properties. In the same way, the in-situ anti-fouling tests of copper and bronze were performed in Qingdao for 8 years. Successively, the anti-fouling properties were analyzed combining with the electrochemical process of copper alloy corrosion and biology process of the adhesion. The chemical, physical and biological factors influencing the fouling properties of copper alloys were also investigated. The results showed that the coppers can equip themselves with antifouling performance by producing some toxic substances during the processes of chemical and electrochemical reaction. In addition, the antifouling ability was proved to relate to the exfoliation effect, which was the result of interaction between stain layer adhesion and spalling force of the attachments.