Abstract 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.

Abstract 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.

Abstract 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.

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.

Abstract 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.