Humidity can also be a factor, so it is worth checking whether a coating can be applied at the environment’s humidity level. Flash corrosion can also occur where moisture is present on bare metal surfaces, this corrosion can continue beneath the surface of a newly-applied coating. Although some coatings use a second layer to cover these pinholes, moisture can also negatively impact drying times. Wet surfaces can cause pinholes to develop during the curing process as moisture evaporates from between the surface and the coating, forming small holes. 6. Dry the SurfacesĬoatings work best with surfaces that are dry. A correctly profiled surface, tailored to the coating process / material, will offer improved adhesion and mechanical bonding. New coatings may require a new surface profile than the original coatings. Once any loose materials and other substances have been cleaned from the surface it is important to profile the surface itself. This can be achieved by techniques such as abrasive blasting, which will efficiently remove rust, mill scale and other loose parts from the surface of the substrate. The surface of the material itself will also need cleaning of any loose parts that may flake or crumble. Chlorides can cause rates of oxidation in metal to increase, meaning that corrosion damage will occur sooner this is known as chloride induced corrosion.īecause these types of surface contaminant can be invisible to the naked eye, testing may be required to determine their presence. This is particularly prevalent near the sea or other marine environments. Many surfaces in industrial settings come into contact with oils, grease and other lubricants, all of which need to be removed so as not to compromise the bond strength between the substrate and the new coating.Ĭhlorides can also accumulate on a material’s surface as they travel through the air. Old coatings are not the only substance that will need to be removed from a material’s surface. 3. Remove Oils, Chlorides, Acids and Other Surface Contaminants Stripping coatings back until there is a clean surface, such as white metal, will help to mitigate problems like corrosion and lengthen asset lifespans. Applying a new coating over an old, failed coating will allow pre-existing problems like bubbling, flaking or peeling to continue beneath the covering layer. Surfaces generally require any old coatings to be removed before a new coating is applied. Surface profilometry may also be beneficial to identify if the existing surface can provide the required mechanical key for subsequent processing steps, although in most cases, some form of surface preparation will generally be required. These grades may help determine if surface preparation will be successful and what techniques are going to be required. Standards can assist with this assessment, such as with BS EN ISO 8501-1, which provides details of rust grades ranging from A-D for steel surfaces. These include: 1. Surface Condition Assessmentīefore any preparation can begin, it is important to assess the condition of the surface. There are several general stages that are followed to successfully prepare a surface for adhesion, coating, welding or other procedures. ContentsĬlick the links below to skip to the section in the guide: While there are different methods of surface preparation for different materials and applications, they tend to follow some set stages. Various surface preparation techniques are used to prepare substrate materials such as aluminium, concrete, plastic, steel and other alloys and wood. Surface preparation can be done either chemically or mechanically to clear the surface of pre-existing coatings, residue, surface imperfections, organic matter, oxidation and other contaminants. Surface preparation is essential for treating steel and other substrates before they are painted, coated or lined. Surface preparation refers to the various methods that can be used to treat the surface of a material prior to coating application, the use of adhesives and other procedures. National Structural Integrity Research Centre.Structural Integrity Research Foundation.
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