Thermal sprayed marine coatings in the marine environment usually encounter chloride-induced corrosion and microbiologically induced corrosion. Formation of microbial biofilm is crucial for subsequent attachment of large fouler and understanding the initiation and growth of the biofilm is essential for possibly controlling the occurring of biofouling. This paper reports the formation of Bacillus sp. bacterial biofilm on arc sprayed aluminum coatings and its effect on the corrosion behaviors of the coatings. Results show fast and pronounced attachment and colonization of the bacteria on aluminum coatings. The bacterial biofilm was systematically examined by CLSM, FESEM, and Raman spectroscopy. Electrochemical assessment revealed that the aluminum coating immersed in the bacteria-containing media showed higher corrosion resistance than the sterile samples. A model was proposed to explain how the microorganisms and their metabolic by-products protect the coatings against penetration of corrosive media. The results would give insight into design and fabrication of thermal sprayed coatings for enhanced anti-biocorrosion performances in the marine environment.

For thermal sprayed coatings, compactness of their constituent particles is required in many applications, e.g. to obtain impermeable anticorrosion coating in marine use. We investigated key factors to improve compactibility of deposited particles in HVOF sprayed coatings by condition measurements of spray particles. The results revealed that plastic deformability of the sprayed particles as well as their molten fraction was important to obtain the dense VHOF coatings.

This paper discusses the performance of arc-sprayed composite layers produced using aluminum oxide-filled wires. In tribological property testing, the composite layers show good non-slip behavior with a high coefficient of friction. They also exhibit excellent wear resistance, four to six times better than that of aluminum layers, owing to the presence of aluminum oxide particles dispersed throughout the metal matrix. Paper includes a German-language abstract.

For very large structures and parts in critical environments, a materials solution often cannot be found by using one material. The specific desired properties for those structures, like stiffness, ductility, high temperature stability, corrosion resistance, etc. are difficult to fulfill with only one material. In this case a solution may be found by using coatings and design their specific properties to replenish each other by their combination. The Thermal Spraying processes offer the necessary flexibility of producing thin to thick, ductile, soft to hard coatings while due to the wide range of process temperatures it is possible to process a wide range of materials, both as coating and structure. In this paper the some recent and important developments in Thermal Spraying to produce coatings for technical demanding structures will be described. These developments consist of High Power Plasma Spraying, powder- and process control development. To ensure process consistency during long spraying times and to apply reproducible coating quality a suitable process control is of great importance and the development of temperature control by Pyrometry and Thermography will be presented. The example will be drawn according to the application of a coating on a ball valve for off-shore and ship diesel engine parts (piston and valve).

Thermal spraying has been used to protect many steel structures from aqueous corrosion using Zinc and Aluminium, and to some extent their alloy coatings to provide galvanic protection. The lifetimes of the coatings can approach 50 years even when exposed in severe marine environments. Zinc coatings work by continuously sacrificing themselves and slowly dissipating over time. Aluminium coatings passivate more readily and form a barrier layer, the passivity makes them less able to protect damaged areas and to self heal. A new ternary coating system involving Aluminium, Zinc and Magnesium has been shown to be capable of providing both a passive barrier layer as well as being able to give galvanically active protection. Salt spray tests have shown that the resistance to red rust of these new coatings increases by 300% over similar thicknesses of the separate metal coatings. Processing by arcspray is straightforward and both adhesion and deposition efficiency are better than where Zinc is sprayed alone.