There are lots of different coating applications and techniques, so here we will try and explain them in details and give answer the questions we get asked all of the time.
Powder coating is a dry finishing process that has become extremely popular since its introduction in North America over in the 1960s. Representing over 15% of the total industrial finishing market, powder is used on a wide array of products. More and more companies specify powder coatings for a high-quality, durable finish, allowing for maximised production, improved efficiencies, and simplified environmental compliance. Used as functional (protective) and decorative finishes, powder coatings are available in an almost limitless range of colours and textures, and technological advancements have resulted in excellent performance properties.
Powder coatings are based on polymer resin systems, combined with curatives, pigments, levelling agents, flow modifiers, and other additives. These ingredients are melt mixed, cooled, and ground into a uniform powder similar to baking flour. A process called electrostatic spray deposition (ESD) is typically used to achieve the application of the powder coating to a metal substrate. This application method uses a spray gun, which applies an electrostatic charge to the powder particles, which are then attracted to the grounded part. After application of the powder coating, the parts enter a curing oven where, with the addition of heat, the coating chemically reacts to produce long molecular chains, resulting in high cross-link density. These molecular chains are very resistant to breakdown. This type of application is the most common method of applying powders. Powder coatings can also be applied to non-metallic substrates such as plastics and medium density fiberboard (MDF).
Sometimes a powder coating is applied during a fluidized bed application. Preheated parts are dipped in a hopper of fluidizing powder and the coating melts, and flows out on the part. Post cure may be needed depending on the mass and temperature of the part and the type of powder used. No matter which application process is utilized, powder coatings are easy to use, environmentally friendly, cost effective, and tough!
Shot blasting is a mechanical cleaning process that uses spheres of material to remove oxides and other debris from the surface of another material. Although less commonly mentioned than sandblasting, shot blasting belongs in the same family of abrasive blasting processes in which sandblasting is categorized. The main difference between shot blasting and sandblasting is that shot blasting uses spherical shot as an abrasive media and a centrifugal wheel for propulsion, while sandblasting uses grains of sand and almost exclusively uses compressed air for propulsion.
Shot blasting works by propelling round materials known as shot media against a surface which in turn removes the contaminants of the surface and also can improve its finish. What type of shot media is used is a very important decision for the shot blasting process. The size and hardness of the shot material will dictate how much surface removal of the material being cleaned will occur. The type of material being cleaned will also play a role in the effectiveness of the shot blasting process. Typically, the shot material and size will be selected depending on the composition of the material whose surface is being shot blasted.
Another important part of the shot blasting process is the propulsion method and the resulting velocity of the shot material. The most common way to propel the shot blasting media is through the use of a centrifugal wheel. To propel the shot blasting media, it is unloaded into a centrifugal wheel. Once the shot blast material has been accelerated by the wheel to the desired velocity, it is expelled from the wheel and into the shot blasting gun. Then the operator or machine holding the shot blasting gun directs the flow of the shot media to clean the material surface.
Many shot blasting equipment cells also include a recovery system. The shot blast recovery system will collect the material shot that has already been propelled and impacted against the material being cleaned and return it to the propelling device to be used again. Shot blast recovery is typically performed through the use of a vacuum.
Zinc spray galvanizing is process where a coating is applied to a steel surface by spraying it with atomized particles of molten zinc. This is done by projecting the particles onto the abrasive surface using a handgun applicator or a special flame. The zinc coating provides excellent corrosion resistance for steel and iron objects and structures used in various environments such as marine, industrial and other unfavourable atmospheric conditions.
This process is suitable for structural components which cannot be dipped into a galvanizing bath due to large size and for objects that would become distorted during hot-dip galvanizing. The method is also used on sections of objects that cannot be accessed by dip galvanizing.
The zinc spray galvanizing process starts with the preparation of the structure’s surface by removing rust, unwanted surface coatings, oil and other contaminants. The cleaning is done using high-pressure abrasive shot blasting, which also roughens the surface. This increases the surface area and ensures a successful adherence of the zinc coating.
The atomized metal particles are then sprayed onto the roughened surface where they attach to the surface and solidify. Several layers are applied so as to build up the coating thickness, with typical values ranging between 80 microns and 300 microns, but thicknesses of 50 to 500 microns are also possible.
Zinc coatings widely used for the protection of finished objects are made from mild, low-alloy and high-carbon steels. The excellent corrosion protection is effective in most atmospheric conditions and also when the product comes into contact with either natural or synthetic corrosive substances. Protection against aggressive environments such as salt spray conditions can be enhanced by applying one or two epoxy paint coats onto the zinc coating.
Wet paint spraying is a traditional surface coating method which is applied using a variety of liquid coatings – such as epoxy, glass flake epoxy or polyurethane – to a previously prepared surface.
Wet paint spraying comes in a range of different colours and can be used on top of a metal or multi-coat systems, dependent on project requirement.
Structural steel is a non-combustible material, which does not contribute to the fire load of a building. However, the strength of the material deteriorates as time passes and heat rises, threatening the integrity of the construction. Thus, it is important that a fire protection system is applied, to ensure that in the incident of a fire, the building is safely evacuated.
In general, a fire protection system offers a fire resisting period – the time needed to evacuate a building – that varies between 30, 60, 90 or 120 minutes. Different types of fire protection systems include boards, sprays, concrete reinforcement, and intumescent coatings. According to the BCSA (British Constructional Steelwork Association), the popularity of intumescent coatings has significantly increased – about 55% – from the 1990’s to the 2010’s.
An intumescent coating is basically a paint-like material which is inert at low temperatures – under 200 ◦C – but reacts with heat. As the temperature rises, during a fire event, the intumescent coating swells and forms a char layer that covers the steel. This char layer is of low thermal conductivity, thus acting as an insulating system. It should be noted that the coating usually expands up to 50 times when compared to the original thickness: for every 1mm of paint applied, the char layer can reach up to 50mm of thickness.
To achieve our 60 year guarantee we enhance our specification during the HZS process and during this ensuring robust thickness testing, this adds far greater anti-corrosive protecting to the substrate prior to our special two stage Architectural powder coating stage