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.

Thermally sprayed aluminum (TSA) has been used in offshore applications for decades, protecting steel structures from seawater corrosion. However, very little work is reported on the performance of TSA when damaged, particularly in deep sea applications. This paper presents the results of a study in which an arc-sprayed aluminum-coated steel sample was subjected to synthetic seawater at 5 °C for 30 days in an autoclave at 50 MPa to simulate 5000 m of water pressure. Discontinuities or “holidays” amounting to 3% of the sample area were drilled into the coatings, exposing the underlying steel to direct attack by the synthetic seawater. After testing, SEM and EDX analysis revealed the formation of a protective Mg-based layer on the exposed steel with negligeable calcium content and no visible corrosion products. The results indicate that TSA coatings can protect steel in deep sea environments even when damaged.

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 Na 2 SO 4 , K 2 SO 4 and Fe 2 O 3 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 Cr 2 O 3 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.

In this study, several thermal spray coatings and reference materials were evaluated for potential use in biomass co-fired boilers. The coatings were applied to T92, A263, and X10Cr13 substrates by HVOF and wire-arc spraying using powder (IN625, FeCr, NiCr) and wire (NiCrTi) feedstocks. Coating samples were examined then tested for 5900 h in the superheater area of a fluidized bed boiler burning a mixture of wood, peat, and coal. The corrosion behavior of the coating and reference materials is reported in the paper and the underlying corrosion mechanisms are discussed.

This paper presents key findings from an ongoing study on the marine corrosion behavior of thermally sprayed zinc and aluminum coatings. Zn, Al, and Zn-Al layers of varied thickness were applied to twelve steel pipes by arc and flame spraying and subjected to different post-spray treatments such as sealing and painting. The pipes are mounted vertically on a test rig in the Pacific Ocean and have been inspected annually to record the appearance and thickness of the coatings. After 7 years, the Zn coatings began to show signs of degradation in the immersed portion of the pipe, although no such changes occurred with Al and Zn-Al coatings. After 18 years, heavily damaged sections of three pipes were removed and new pipe was welded in place. The repaired regions were coated with Al-5%Mg, which has performed well so far.

In this study, detonation spraying was used to deposit commercially available Ni-20Cr and WC-Co powders on SA213-T22 boiler steel. Coated and uncoated specimens were subjected to 50 thermal cycles in a molten salt boiler environment 900 °C in order to evaluate their hot corrosion behavior. Mass change measurements were made at the end of each cycle to assess corrosion kinetics and XRD and SEM/EDS were used to characterize corrosion products. An analysis of the reaction kinetics and the formation of oxide scales is provided in the paper.

This work evaluates and compares the properties of weld overlays and thermal spray coatings produced using different feedstock materials. The mechanical and metallurgical characteristics of the coatings and their performance in corrosion and wear tests are discussed.

This study assesses the effectiveness of wire arc sprayed aluminum coatings for protecting welded super duplex stainless steel (UNS S32750) in subsea applications. Pitting and crevice corrosion tests were conducted at different potentials in recirculated synthetic seawater maintained at 90 °C with an acidity of 7.5-8.1 pH. After 90 days, the samples were examined, showing no signs of corrosion even in areas where coating defects were present.

This work examines the corrosion behavior of cobalt and nickel base coatings produced by APS and HVOF spraying. Laser fusing and sealing are also assessed for comparison as are the corrosion properties of tungsten carbide, chromium carbide, and chromium oxide. All coatings and processes are analyzed by cyclic polarization testing and optical and scanning electron microscopy. Test results are presented and discussed along with the relative merits of each process.

In this study, Ni-20Cr alloy powder was synthesized and deposited on T22 boiler steel by HVOF spraying. Coated and uncoated test samples were placed in a silicon carbide tube furnace and subjected to cyclic oxidation conditions in 900 °C air. Oxidation kinetics were established via weight change measurements and oxidation products were characterized based on XRD and SEM-EDS analysis. The results show that in addition to improving the oxidation resistance of the steel, the Ni-20Cr coatings also reduced spallation due to the formation of a protective Cr2O3 phase.

Ion vapor deposition is a physical vapor deposition process often used to apply pure aluminum coatings to aerospace parts for corrosion protection. These coatings, however, are vulnerable to damage during manufacturing and use, leaving the underlying material susceptible to corrosion. The aim of this study is to develop an economical and practical technique for the repair and restoration of damaged aluminum IVD coatings using available cold gas dynamic spraying equipment. Based on the porosity, surface finish, adhesion strength, and corrosion performance of the repair coatings, cold gas spraying is shown to be a strong candidate for restoring damaged aluminum coatings on aerospace parts.

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.