Thermal spraying is a category of surface engineering widely used in many types of manufacturing and structural steelwork industry. It has nothing to do with the injection of thermal insulation foams into the walls of buildings to reduce heat loss and conserve energy.
Owing to the noise, dust and fume generated by the process together with the increasingly stringent health and safety legislation imposed on its operations, there is an increasing trend for thermal spraying to be regarded as a ‘special process’ best sub-contracted to thermal spraying contractors.
Thermal spraying contractors tend to specialise in either anti-corrosion zinc and aluminium coatings, or the many kinds of coating applied to machine elements.
Anti-corrosion thermal spraying contractors are equipped to enable either on-site or in-house blasting and spraying of many kinds of structures ranging from bridges, oil rigs, chemical tanks and their supporting structures. Sometimes anti-corrosion processes are for logistical reasons best undertaken by the manufacturer, rather than thermal spraying contractors, as part of a production line, notably the coating of cast iron gas and water mains pipes, or industrial gas cylinders, where in such cases, a thin layer of zinc greatly increases the working life expectancy.
Machine element work of small or irregular batch quantity is usually sent to thermal spraying contractors who by applying wire or powdered materials through specially designed equipment can deposit a wide range of coatings to meet many kinds of required surface properties such as abrasion resistance, high or low friction, electrical and thermal conductivity / resistance or abradability, where the coating is deposited as a sacrificial layer to protect an expensively machined underlying component such as a gas turbine rotor or turbofan cowling. In such cases thermal spraying contractors will apply the coatings to processes contained in drawings or specifications laid down by the prime manufacturer, but increasingly, thermal spraying contractors are asked to recommend or develop coating systems as a response to problems encountered by designers.
In many cases, coating surface properties are enhanced by appropriate finish machining or grinding operations which are often developed in conjunction with manufacturers by thermal spraying contractors.
