What is powder?
The process of powder coating was invented 1945 by American Daniel Gustin and patented the same year.
Powder Coating is a type of coating that is applied as a free flowing, dry powder, not containing any harmful VOC’s.
Unlike liquid paint systems which are applied using an evaporating solvent, Powder is applied electrostatically and then cured under heat, when the curing cycle is complete and the component cooled down it is ready for use, with a coating which is harder and tougher than liquid paint systems.
Because Powder Coating does not have a liquid carrier, it can produce thicker coatings than liquid paint systems without running or sagging, and have a much quicker stoving schedule than liquid paint.
Overcoating Powder and PVCu
Over the period many years we have developed an ongoing and mutually beneficial partnership with several major aluminium fabricators.
We can powder coat lengths up to and including five metres in length.
We have recently in conjunction with a paint applicator in the Midlands, after lengthy trials, developed a wet paint coating that can be applied directly to powder coated items and PVCu and hard plastic components.
Unlike most paints for plastics which try to stick to the substrate, this coating forms a molecular cross bond with the surface.
The paint is available in the all standard RAL and BS colours.
This capability enables us to produce dual colour extrusions, which is attractive to conservatory, double glazing, and roof manufacturers.
There are no problems applying the material on site and we offer a five-year warranty against fading.
These include masking and spraying of extrusions to create dual colour for use particularly on conservatories, and total resprays over powder coated extrusions to change to a special colour or to use the clients stock, thus saving a substantial amount of money.
How is Powder Applied
The Powder Coating process involves three basic steps:
Removal of oil, dirt, lubrication greases, metal oxides, welding scale etc. it is essential prior to the powder coating process.
It can be done by a variety of ways, HPC (South) would normally shot blast or the items galvanised to treat correctly.
The most common way to apply the Powder Coating is by utilizing an electrostatic gun. The unit is first earthed, and a very high charge of electricity passed through the unit.
The gun imparts a negative charge to the powder which is the sprayed towards the work piece using compressed air and then accelerated by the powerful electrostatic charge.
Although it appears to be a normal coat of paint, it has been engineered to experience a chemical reaction when exposed to intense heat (for example in a fire) into a layer of protective fireproofing.
The increase in temperature will cause the coating to expand to many times its original film thickness, the expansion factor can be as much as 100 times. The result of this reaction will cause the coating to form a foam like surface on the item, this surface will offer protection against deformation and thus structural failure of the steel, or fire on any timber sections that are coated.
In tower blocks, offices, etc. it will give the occupants time to leave the premises. The coating had not been maintained on the Twin Towers.
The film thickness applied and the paint formulation determines the length of time that the fire will be contained, this is normally 30 minutes, 60 minutes, or 90 minutes.
Before the coating is applied several tasks need to be completed. A full set of drawings needs to be supplied to enable the areas of each section to be calculated, also the fire retention period needs to be supplied. From this information, we will be supplied from the paint manufacturers with the dry film thickness required to achieve the specification required.
Due to the high paint thickness that is needed to be generated the paint thickness it is a multi-coat process, this can be achieved with a spray gun or roller. Because of the extreme film thickness along with the paint formulation the finish is not smooth, orange peel and possibly sags will be apparent when inspected. Being normally structural steel components, this will be acceptable because they will be in the heart of the building and not visible.
Three key components are bound in a solvent or water-borne polymeric binder, the expansion process is caused when these components interact. These components are;
Acid source: ammonium polyphosphate.
Expanding agent: melamine.
Carbon supplier: polyols as starch, pentaerythritol.
Powder Coating Ingredients
How does the Powder stay in place during the coating process?
Moreover, how are you able to obtain some of the beautiful vibrant colours that are associated with Powder Coating.
It all comes down to what is in the Powder below is a very basic list of ingredients.
This is the foundation for the Powder it comes in two distinct types to yield a specific finish either polyester or epoxy.
These are for things like colour, matt finish, and hardening properties.
Prevent the powder from clumping, they what give the powder its evenness.
These define the finished colour Powder after its baked and cured.
Are what cause the Powder to harden and bond with metal during the baking process.
They give the cured coating a glossy durable finish.