The Metal Spray Process involves heating of the material to be applied and projecting it onto the substrate no solvents or chemicals are used.
The process has been used in every conceivable industry including Aerospace, Automotive, Biomedical, Agriculture, Space travel, Power Generation, Construction, Mining and so on. The metal/thermal spray process is a coating procedure used to change the surface properties of a part by adding a layer(s) of material to increase many factors:
Dr Max Ulrich Schoop (pictured above) pioneered metal spraying in the early 1900’s when he discovered molten lead and zinc would stick to almost any surface when firing pellets out of a toy cannon he had bought as a gift for his young son !!!!
The materials use in this coating procedure can be:
Substrate materials include:
The process of Metalspraying, Thermalspray, and Spray Galvanising all of which and others refer to the same process has been in existence since the early 1900’s and is a process used worldwide.
The Metalspray process involves the melting of a wire (Zinc in this case) and projecting it by compressed air onto the work piece to provide a coating that can be tailored to suit the environment into which the component will be located.
NO! It only uses a heat source through which a powder or wire is fed, melted and projected onto the substrate.
Metalspraying offers the following advantages:
No it is not necessary to paint the coating afterwards however in doing so and correctly applied it can enhance the life of the coating further , plus we can’t get Red or blue or …. Zinc, Aluminium, etc.
Metalspraying offers the following advantages over painting:
Compared to Electroplating Metalspray offers:
Yes the Flame, Arc and HVOF processes can all be operated on site as they are available in mobile forms. Standard Health & Safety procedures need to be applied after undertaking a site risk assessment as with any other process to be used on a site scenario.
Yes over the years the Metalspray Industry has developed International standards (ISO) as well as regional standards based upon the International ones. The standards cover such things as:
If you are applying and Anti corrosive coating Zinc , Aluminium or one of their alloys to a substrate then the surface would need to be clean and dry and then Grit blasted . If an Engineering coating is being applied then the component should be de-greased, pre -machined normally by turning a rough thread.
If the component has been in service running in oil then pre heating the component to between 260° C and 370 °C and maintaining this temperature until oil ceases to come to the surface or until all smoking stops will satisfactorily clean the component.
No, the media to be used for surface preparation should be:
Generally speaking there is no limit; however from a practical point of view excessive coating thickness is unnecessary. In some cases the coating thickness maybe determined from standards that will give life expectancy until first maintenance in other cases it can be the requirement necessary to restore a part to its original condition.
The International Standard BS EN ISO 2063 as well as AS/NZ 2312 gives recommendations of coating thickness and time until first maintenance.
In North America the Metalspray process is known as “metallizing” or “Thermal Spray” with early work being carried out by the American Welding Society (AWS) who in 1953, exposed panels coated with flame sprayed zinc and aluminium and various sealers. Very favourable results were reported after 19, 34 and 44 years of exposure at coastal and industrial sites. This work was followed up by the US Army Corps of Engineers with successful trials of Metalspray as a more abrasion resistant coating than vinyl on dam gates, and which resulted in a comprehensive design manual (USACE, 1999) which is available on the internet.
The US Federal Highway Agency noted (FHWA 1997) that work by the AWS and US Navy showed that “properly applied metallized coatings (zinc, 85% Zinc/15% Aluminium, and Aluminium) of at least 6 mils thickness provide at least 20 years of maintenance free corrosion protection in wet, salt-rich environments and are expected to provide 30 years of protection in most bridge exposure environments”. The FHWA has sponsored several research projects coating steel bridge beams with TSM, including one of environmentally acceptable materials which found that the thermal sprayed zinc (TSZ) systems were the best performing over 40 coating systems tested (which included top coated and single coat “high-ratio” and other inorganic zinc silicates) with no undercutting at scribe marks after 6.5 years exposure, and had the lowest Life Cycle Cost.
Thermal Sprayed Aluminium (TSA) has been widely used in offshore oil and gas industry and by 1997 over 400,000 sq. metres of TSA had been applied to oil platforms in the North Sea to provide corrosion protection to flare stacks, riser pipes in the splash zone and submerged tethered legs (e.g. Conoco’s Hutton platform built in 1984). Experience indicated that TSA coatings, when properly applied and with the use of specific sealer systems, will provide a service life in excess of 30 years with zero maintenance required.
In short, the years of testing and results which have accumulated into the various standards demonstrate the coatings ability to withstand the harshest of environments and to with stand the test of time.