The advantages of UV-curing polymers are well known and used in various coating and adhesive applications. Curing times of a few seconds and long application windows allowing an increased throughput in series production. The use of UV-curing polymers in sealers is beneficial, but so far insufficient due to only surface curing. With a newly developed dual-cure mechanism in sealers, it is now possible to combine deep penetration curing and surface curing. The hybrid sealers combine radical polymerization with subsequent polyaddition or polycondensation. The development of sealers for thermal sprayed (TS) coatings involves an extensive requirement profile. This includes properties such as corrosion protection, penetration depth and processing times. High penetration depths of the sealant into the coating system are important to ensure a protection over the full lifetime of the TS coatings. The depth of penetration of the developed sealers into various TS coatings was determined by measuring the gas permeability in a specially developed test procedure. The corrosion protection effect in combination with TS coatings was determined by measuring the cell voltage. In summary, two UV dual-cure sealers have been developed to seal TS coatings with deep penetration and corrosion protection.

In this study, dicalcium silicate (Ca 2 SiO 4 ) coatings were deposited on stainless steel substrates by atmospheric plasma spraying. Salt spray and immersion tests were carried out to evaluate corrosion performance and XRD, SEM, and EDS were used to analyze phase composition and microstructure. During corrosion testing, calcium carbonate crystals appeared on coating surfaces and the pores were filled with hydration products, producing denser coatings. Potentiodynamic polarization curves and electrochemical impedance spectroscopy plots indicated that the corrosion resistance of the coatings increased after immersion in saltwater and artificial seawater, and in the latter case, a silica-rich layer was observed between the coating and the calcium carbonate crystals.

300M steel is one of most important aerial materials, which can be used for landing gear and flap & slat track. Some surface engineering technologies are needed to be adopted on its surface, because of its bad corrosion performance. WC10Co4Cr Coatings by high velocity oxygen-fuel spray processing (HVOF) is an environmental friendly method for this protection. In this paper, WC10Co4Cr coatings were prepared on 300M by optimized HVOF processing. And their corrosion performance has been estimated by neutral salt fog test, according with ASTM B117. The results indicate that the porosity gets larger and the hardness gets higher for the dissolution of bonding phases after the test. And for the optimized coatings, there are no corrosion products in the surface and interface between the coating and 300M steel, after 2000 hours ASTM B117 test. So the coatings have a good corrosion performance.

Higher operating temperatures coupled with biomass-derived fuels can lead to aggressive corrosion damage to the superheater/reheater tubes in power plants. In this study, a HVOF sprayed NiCr coating was deposited onto a 9 % Cr substrate, which were exposed in simulated coal-biomass combustion gases with a screening deposit containing Na2SO4, K2SO4 and Fe2O3 at 700-750°C for 1000 h. The tests were carried out using the “deposit-recoat” test method and pre and post-exposure dimensional metrology was used to quantify the coating damage in terms of metal loss distributions. The exposed samples were also examined in a SEM/ EDX. The coatings developed a protective Cr2O3 layer at the coatings/ deposit interface and a Cr depleted zone was observed underneath the oxide layer. NiCr coating provided suitable corrosion protection with a median metal loss of ~35μm in 1000h.

Due to the demand for improved fuel economy as well as increased safety features, weight reduction is one of the major aims in the automotive industry. Future lightweight automotive components for the next car generation will probably use lots of magnesium alloy. These will form galvanic couples with other materials and may induce phenomena accelerating the corrosion rate of automotive components. The materials used were magnesium alloy AZ31B and several types of cold sprayed coating. The relative performance of each cold sprayed corrosion preventive compounds (CPC) was assessed in combination with the materials under several different electrochemical and accelerated corrosion tests. Baseline data for AZ31B with no CPC applied was also collected. CPC characteristics and properties are also included and discussed. The studies on bare Mg/Steel couples validated accelerated corrosion but found that CPC cold sprayed coatings mitigate corrosion rates. Thus Mg/Fe interfaces with defect-free cold sprayed coatings CPC can prevent buildup of corrosion products and reduce galvanic corrosion of automotive components.

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.

Intermetallic TiAl coatings were applied to ferritic steels using plasma and HVOF spraying methods. The specimens were then placed in reducing sulfidizing atmospheres for high-temperature corrosion testing. This paper describes the experiments that were performed and presents and analyzes the results. In general, for the reasons given, the coatings performed better in an Ar-H 2 -H 2 S-atmosphere than in one containing CH 4 . Paper text in German.

The application of HVOF spraying to deposit high quality coatings of corrosion resistant alloys for protecting an underlying steel substrate against corrosion in seawater has received much interest over the past few years. Despite the attainment of low levels of porosity and oxide, the coatings to not appear to offer the same level of corrosion resistance as the corresponding bulk materials. The aim of the work reported here is to demonstrate the level of corrosion performance that can be expected from coatings of corrosion resistant alloys deposited using the HVOF spraying process. Three alloy types are considered, a stainless steel with a composition similar to 316L, a nickel alloy with a composition similar to 625 alloy, and commercially pure titanium.

Thermal spray committee of Japan Association of Corrosion Control (JACC) has been conducting a corrosion test of thermal sprayed Zn, Al and Zn-Al coatings at coastal area since 1985. Twelve kinds of sprayed coating were deposited onto steel pipe by arc- and flame-spraying at varied thickness and subjected to various post-spray treatment. The samples were set vertically into the seawater at a port 80 km south from Tokyo. Corrosion performance were inspected annually by recording the appearance and coatings' thickness at sea air-, splash- and tidal-zones. No significant changes were observed for five years exposure. After 7 years, however, Zn coatings with and without sealing started to suffer degradation in the immersed portion. Contrary to this, Al and Zn-Al coatings still exhibit superb corrosion performance. The test will be continued till 2001 to finish a 15 years field test. This paper reports the summary of corrosion performance of sprayed coating during the first 10 year period.

Hot dip galvanized zinc coatings on steel structures are known to have superior atmospheric corrosion resistance properties compared to painted structures. However, the zinc coating can not be applied by this method on large steel structures. The protection of large steel structures against atmospheric corrosion is traditionally done by painting. The environmental pressure to eliminate solvent based paints has forced the painting contractors to move towards water based paints or completely rethink the coating process. One solution to this problem is to use arc sprayed zinc as the "primer" and water based paints as a sealer and a top coat. The research and field tests conducted and supervised by VTT has produced promising results that are described in the paper. The possibility to apply water based paints directly over the arc sprayed zinc is discussed and results of field and laboratory tests are given. The economic aspects of both water based and traditional paint systems over the arc sprayed zinc are discussed in the paper.

Structural damage caused by corrosion in concrete structures is widespread and requires extensive repair work. The installation of corrosion protection systems for constructions that are under unfavorable conditions is urgently necessary. Thermally sprayed coatings serving as anode have been developed from the cathodic protection of steel. These systems have attracted attention because of their performance and lower cost advantages, and they are about to enter the competitive anode system market. Thermally sprayed zinc coatings are applied to the surfaces of steel-reinforced concrete components that are affected by corrosion. In this article, the ability of the system to deliver a protective current is verified by field tests in a marine structure in the Arabian Gulf that was discussed in 1997. Paper includes a German-language abstract.

The use of the wire arc spray process for the production of zinc and aluminum coatings as corrosion protection represents a rapidly growing market. In this paper, the effects of various spray parameters on the performance of the process for these materials are examined. The effects of arc voltage, current, and wire diameter have been studied for their effects on the main factors affecting process performance, spray performance, and application efficiency. The results of this study have led to the development of a spray system or a power supply to maximize the performance of the process for corrosion protection applications. Paper includes a German-language abstract.

Thermal sprayed ethylene methacrylic acid (EMAA) and ethylene tetrafluoroethylene (ETFE) coatings were evaluated for corrosion protection in a biochemical process to treat geothermal residues. Coupon, Atlas cell, peel strength and cathodic disbondment tests were performed in aggressive environments including geothermal sludge, hypersaline brine and sulfur oxidizing bacteria ( Thiobacillus jerrooxidans ) to determine coating suitability for protecting storage tanks and reaction vessels. It was found that the polymers were resistant to chemical attack and biodegradation at the test temperature of 55°C. The EMAA coatings protected 3l6L stainless steel from corrosion in coupon tests. However, corrosion of mild steel substrates coated with EMAA and ETFE occurred in Atlas cell tests that simulated a lined reactor operating environment and this resulted in decreased adhesive strength. Peel tests revealed that failure mode was dependent on exposure conditions. Cathodic disbondment tests in brine at room temperature indicated that EMAA coatings are resistant to disbondment at applied potentials of -780 to -1070 mV SCE for the test conditions and duration.

Primarily thermal-spray coatings have been developed to combat excessive degradation of components due to mechanical wear. However, these coatings are increasingly being required to function in aqueous environments where corrosive attack is possible. The durability of thermal spray coatings in terms of corrosion resistance is the focus of this paper. Two coating methods were studied: high-velocity oxyfuel (HVOF) and thermal spray-fused. The HVOF coating was WC-Co-Cr and the spray-fused coatings were WC-Co based and Ni-Cr-Si-B. Samples have been exposed to aqueous environments at a range of different temperatures and of varying salinity (500ppm and 35,000ppm Total Dissolved Solids) in order to simulate freshwater and seawater environments. The detailed material loss and degradation mechanisms have been investigated using electrochemical-monitoring techniques supported by precise post-test microscopical examination using light microscopy, scanning electron and atomic force microscopy and x-ray microanalysis. The study has demonstrated that there is a strong dependence on coating durability for all the coatings as a function of temperature but salinity has a lesser effect. However there are interesting differences in the extent and detailed mechanisms of such effects between the different coatings.