The performance and, as a consequence, the application of functionalized fiber-reinforced plastic (FRP) are limited due to low adhesion strengths between the metal coating and the polymer-based substrate. Common pre-treatment methods, to successfully apply a metal coating by thermal spraying on commercial FRP, are mechanical blasting, etching or thermal treatment. Moreover, additional layers made of metal wire or sand have been integrated into the FRP surface. A promising material-sensitive pre-treatment method for FRP substrates is laser micro structuring. This method avoids uncontrolled damage of surface-near fibers and offers an increased interface area. Unique for pulsed laser structuring is the opportunity to achieve a clamping effect between the functional coating and the FRP by a trench-like structure.

Tailoring strength and ductility in additive manufacturing or repair is key to successful applications. Therefore, cold spraying must be tuned for maximum amounts of well-bonded internal interfaces as well as sufficient softening of the highly workhardened deposit. Zinc (Zn) with its low melting temperature is an ideal model system to study phenomena associated with high strain rate deformation and local temperature distributions, both, in single impacts and thicker deposits. Bonding and recrystallization can be facilitated by covering selected wide parameter regimes in cold spraying. Despite the low temperatures, Zn single splats already show recrystallization at internal interfaces, the respective amounts then scaling with increasing process gas temperatures. At higher process temperatures, deposits are almost fully recrystallized. The recrystallization seems to improve bonding at internal and at deposit-substrate interfaces. Under optimum conditions, an ultimate deposit cohesive strength of up to 135 MPa and an elongation to failure of 18.4% are reached, comparable to that of laser-manufactured or bulk Zn parts. This demonstrates a welltuned interplay between high amounts of bonded interfaces and softening by recrystallization that allows for deriving bulk-like performance of cold sprayed material without additional posttreatments. Correlations between microstructures, mechanical properties, and fracture mechanisms supply information about prerequisites needed for reaching high ductility as obtained in damage and failure modes of deposits and bulk materials in global and local approaches.

Zinc oxide (ZnO) is known for its rich diversity of microstructures and has been attracting attention for its unique combination of mechanical and physical properties. It has been a material of interest in different areas such as optoelectronics, sensors and the general ceramic industry. It also has been a material of interest in biomedicine due to its antimicrobial characteristics and biocompatibility properties. A simple processing route to produce ZnO micro/nanostructures is the thermal oxidation of zinc, which results in a wide range of ZnO nanostructures depending on the oxidation conditions. The main objective of this study was to investigate the influence of a severe plastically deformed zinc microstructure on the formation of ZnO nanostructures produced by oxidation, with a special attention to the zinc oxide growth mechanism and nanostructures characteristics. For this purpose, the cold spray process was used to produce Zn coatings using different feedstock powders that required different process parameters in order to obtain Zn coatings with severely deformed particles. A non-catalytic thermal oxidation method was then used to successfully produce ZnO nanostructures at the surface of the heavily deformed cold sprayed Zn coatings. The as-grown ZnO nanostructures were investigated in detail using scanning electron microscopy and X-ray photoelectron spectroscopy. These investigations revealed that the chemical fingerprint of the oxides grown in the cold sprayed samples was different from that of conventional ZnO. It was also observed that in the oxidized cold sprayed Zn coatings, the formation of ZnO nanowires was hindered due to the formation of blisters generated during the high temperature exposure, revealing nonoptimized process parameters.

Cold spraying is a semi-empirical method in that spray parameters must be optimized experimentally in regard to coating quality and deposition efficiency. In this work, porosity and deposition efficiency are the key parameters in the optimization of corrosion-resistant zinc coatings produced by high-pressure cold spraying. The deposition process is described along with the tests used to assess the morphology, adhesion, and anticorrosion properties of the coatings obtained.

The coatings of zinc and its alloys are broadly used to prevent the rusting of substrate surfaces such as steel. Cold gas dynamic spray (CGDS) is an innovative coating technique in which the deposition of solid powder particles depends upon the kinetic energy of the particles rather than thermal energy. Therefore, application of cold spray is to provide superior rust resistance by depositing more materials, formation of passivation layer, and cathodic protection. In this study, numerical investigations on zinc micro and nano size particles in CGDS were carried out. The height of the injector, the expansion ratio and the diameter of the inlet of the de-Laval nozzle was varied systematically by optimizing the stand-off distance using the two-dimensional axisymmetric models of CGDS, to study their effects on the velocity and the distribution of the particles. Prediction of the deposition efficiency was carried out using the various critical and erosion velocity models.

By means of In-Mold-Metal-Spraying (IMMS), wire arc sprayed metal coatings are transferred onto plastic parts during the injection molding process for the efficient production of metallized plastic parts. One potential field of application of IMMS parts are electrical applications such as electrically conductive tracks or electromagnetic shielding. In the current study, the properties of the transferred coatings, especially the electrical resistivity, are determined. Different feedstock materials are used for the application of the coatings. In the first investigation, pressurized air is used as atomizing gas for wire arc spraying. In contrary to Zn coatings, Cu coatings applied with pressurized air have a significantly higher electrical resistivity in comparison to massive copper. One possible reason for this is the oxidation of the Cu particles during the spraying process. Therefore, N 2 and a mixture of N 2 and H 2 are used as atomizing gas to reduce the oxidation of particles. Consequently, the electrical resistivity of IMMS parts can be significantly reduced. Furthermore, spraying distance, current and pressure of the atomizing gas are varied to investigate the influence of these process parameters on the coating properties.

This study investigates the feasibility of using solution precursor plasma sprayed (SPPS) zinc oxide to fabricate NO 2 gas sensors. In the experiments, thin ZnO layers were deposited on Al 2 O 3 substrates that had been printed with interdigitated gold electrodes. FE-SEM images show that the as-sprayed films are highly porous and nanostructured as desired. Diffuse reflectance measurements reveal that significant absorption occurs in the visible light range. In gas sensing tests, the SPPS ZnO films were responsive to concentrations of NO 2 gas down to 0.4 ppm. The performance is attributed to the porous nanostructure and the presence of oxygen vacancies, or mid-bandgap defects, as confirmed by XPS analysis.

A new process called in-mold metal spraying (IMMS) shows good potential for producing metallized plastic parts quickly and inexpensively. A zinc layer is deposited on mold cavity inserts using wire arc spraying and subsequently transferred to a plastic carrier via injection molding. Finely adjusted bonding strength between the carrier body and coating is essential for successful coating transfer. To that end, this study evaluates the influence of carrier body surface pretreatments on the transferability and bonding strength of zinc coating. Carrier bodies made of different types of steel pretreated by glass bead blasting and EDM were tested and their surface topography examined. In the initial experiments, the hardness and surface topography of carrier bodies were identified as factors that can influence coating transferability. Further experiments focusing on the adhesion strength of zinc on hardened and annealed carrier bodies were conducted to verify the influence of hardness on bonding strength.

This paper describes a new composite coating technology developed for hot dip galvanizing rolls used in automotive manufacturing. The multilayer coating consists of HVOF sprayed WC and electroless Ni-P plating. Coating surfaces and cross-sections are examined and adhesion strength, friction, and wear resistance are measured. In addition, changes in surface roughness are recorded on galvanizing rolls after three months of service.

Thermally sprayed coatings of zinc, and in particular zinc-aluminium alloys, offer maximum corrosion protection for steel structures and reinforcing steel in concrete. They are primarily produced by arc or flame spraying. The surfaces of zinc and zinc alloy spray coatings can be protected by sealing top coats. This produces an optimum combination of passive and active corrosion protection and allows a service life of over 20 years. The development of new materials assumes intensive investigations. This paper provides an overview of the properties of thermally sprayed zinc and zinc-aluminium alloys as well as their microstructure and investigates the corrosion protection effect in tests and near-practical conditions.

A design of experiments approach was used to characterize process-microstructure relationships in the twin wire arc process using zinc feed stock. Specifically, the effect of arc current, primary atomizing gas pressure, secondary atomizing gas pressure, and standoff distance on deposition efficiency, spray pattern shape, atomization behavior, coating porosity, and coating surface roughness were investigated. All work was conducted using a Praxair 8835 torch spraying 02Z zinc feed stock. It was found that primary and secondary atomizing gas pressure significantly affected spray pattern shape, atomization behavior, coating porosity and coating surface roughness. Arc current significantly affected spray pattern shape. Standoff distance significantly affected deposition efficiency, spray pattern shape, and surface roughness. Discussion will focus on using the relationships identified through this experiment to tune the wire arc process.

Zn coatings have been applied on steel substrates used by Renault for the manufacturing of car bodies. We had the task to make these on-line thin coatings on smooth and non de-oiled surfaces with a translation speed of 1 m/s. Furthermore, in certain cases, these coatings were situated on a visible surface of the car body and on a precise position. The coating process must be adapted to the clean conditions of the current automotive industry. The development of this application has been focused mainly on the study of a new zinc powder grade as well as on the projection procedure which had to adapt to the constraints and to the productivity of an automotive manufacturing line. Cold Spray addresses all these requirements. Positive results obtained on the mechanical examinations, the accelerated corrosion tests and chippings tests demonstrate that such new coatings meet the specifications of the customer for this kind of processes.

Zn, Zn-Al and Zn-Mg coatings have been produced by cold spraying. By careful tuning alloy compositions and spray conditions, dense coatings are produced with a hardness of 200 HV0.01 that are up to four times harder than pure bulk Zn, thus meeting the requirements for print applications. These new developments open opportunities for producing harder and more wear resistant coatings, which may allow for the production of larger number of copies without compromising quality.

Thermal spray of Zn, Zn/Al, or Al is extensively used to make anticorrosion coatings on steel structures. Twin arc spray and wire flame spray are the two most practised processes to achieve such coatings. This paper presents measurements of particle emissions generated by these two processes. Sampling and analysis of aerosols generated by both processes have been carried out inside the exhaust ductwork using various instruments: an ELPI impactor, a CNC (Condensation Nucleus Counter), a TEOM microbalance and sampling filters allowing sampling for SEM observations. Electric arc spraying produced much more fumes of ultra fine particles than flame spraying. Aluminum spraying also produces large fume quantities compared to the Zn spraying under the same conditions. The aerosol comprised submicron particles and 95% of the numerical particle size distribution was less than 100 nm. The nanometric nature of the fume particles was confirmed by observations on the SEM. The strong dilution caused by compressed air has the effect of strongly limiting particle coagulation and, in turn, the size of the agglomerated particles. Electric arc spray has taken market share versus wire flame spray for Zn, ZnAl, or Al spraying, but this study shows that it generates much more particle emissions.

Cold spray produces superior coatings with many unique properties, which have led to many new applications of sprayed coatings. In a few applications, such as in-situ repair of aircraft body/engine parts, etc., a portable system is required. Though some portable low pressure (5 – 10 bars) systems are available, these systems have many limitations on coating materials and coating qualities. Recently a ‘Portable high pressure cold spray system’, called Kinetiks 2000, has been developed. Kinetiks 2000 system can operate at 400 °C max nitrogen temperature and 20 bars max gas pressure. A touch panel on the console is used to input and control the process parameters. A hand held gun with a filament heater and a gun body, mounted directly onto the heater, is used for manual spray. This system operates with two different powder hoppers. Coatings of many materials, including aluminum, copper, titanium, zinc, etc have been produced. Microstructural investigations of sprayed coatings have shown that good, strong, dense coatings with clean interfaces and strong bonding to various substrates can be produced. Experiments are continuing to quantify the process characteristics and record the properties of sprayed coatings.

The present work probes the deposition of metallic coatings on high fiber volume fraction carbon/epoxy polymer matrix composites using pulsed gas dynamic spraying. Well-consolidated and well-adhered coatings of zinc and copper were successfully applied and initial trials with higher melting point metals have been promising. Two key aspects of the technique are the low temperatures involved and the presence of embedded ductile particles in the substrate. The embedded particles promote adhesion and eliminate the need for surface preparation procedures along with associated risks. The hardness and porosity of the zinc coatings deposited on polymer matrix composites were found to be comparable to that of similar coatings on metallic substrates.

Ductile iron pipes (DIP) have been used worldwide since 1960s for water transmission and distribution mains. By 1979, ductile iron pipe largely replaced cast iron as the predominant material in water industry. Zn and Zn/Al 85/15 coatings applied by thermal spray technique are used for the protection of the ductile iron pipe against corrosion in heterogeneous soil conditions. In this study, heat treated and non-heat treated ductile iron pipe samples were coated with Zn and Zn/Al 85/15 in optimum spray parameters by twin wire electric arc (TWEA) spraying technique. The coatings were investigated by optical microscopy, scanning electron microscopy (SEM), and analyzed by energy dispersive spectrometer (EDS). Both Zn and Zn/Al 85/15 coatings showed fairly good lamellar structure with acceptable amount of internal porosities and oxides. Annealing oxides available on pipe surface helped the bonding of coatings. The protection performance of the coatings was compared with accelerated corrosion (salt spray) test according to the ASTM B 117 and corrosion products were analyzed by SEM and EDS technique. Salt spray test results showed that Zn/Al 85/15 coatings have better corrosion resistance than Zn coatings and annealing oxide on ductile iron pipe acts as a good corrosion resistant protective layer.

Twin wire arc sprayed Zn, Al and Zn/Al 85/15 coatings were investigated for comparison of their corrosion resistance, electrochemical behavior. The Zn, Al and Zn/Al 85/15 coatings possess prominent electrochemical passivation behavior. Oxide formation mainly onto the coating surfaces were identified with energy-dispersive X-ray analysis and were believed to be responsible for the passivation phenomena observed in the electrochemical polarization. Zn and Al are more negative in electrochemical potential than iron. Zn coatings act as a sacrificial anode and providing cathodic protection. Aluminum shows passive corrosion protection according to stable oxide layer occurs on coating surface. Zn/Al 85/15 coating show two corrosion protection mechanisms together. In this study, steel samples were coated with Zn, Al and Zn/Al 85/15 in optimum conditions by wire arc spraying technique. These coatings were investigated behaviors of polarization and corrosion resistance with electrochemical test.

Zn and Zn/Al coatings were manufactured by using twin wire arc spray (TWEA) system under various gas pressure and current. Microstructure, hardness, surface roughness and adhesion strength of the coatings were investigated by using standard characterization methods. Test results show that increasing atomizing gas pressure increased mechanical properties and surface quality. The process current had an important role on microstructural, mechanical properties and surface quality.

Hydrogen embrittlement in high strength marine structural steels can occur by improper cathodic protection. In this article the possibility of Hydrogen embrittlement (HE) in high strength steels caused by zinc and aluminium thermal sprayed (TS) coatings has been considered. Provided potential from the TS coatings in marine environments and permissible potential for performing cathodic protection and inhibiting HE has been described. Also effective parameters on HE and prevention methods for HE by thermal sprayed coatings has been reviewed. An effective method for quality stabilizing and potential regulating in anticorrosion TS coatings is utilization of the alloyed materials. Most used material for anticorrosion TS coatings is aluminium that provides relatively moderate potential and low current density and in particular situation can cause HE.