After your parts are disassembled, you need to do a thorough clean of these to remove all dirt, oil, grease, and grime. We ask the client to do this if possible, as this helps us to avoid unwanted contaminants within our facility.
A general degreaser may be used for this cleaning; just make sure it is safe for the part you are working with.
Do not worry about rust or paint at this point, as this will be removed by us.
After you have given your part(s) a thorough cleaning, we will then remove any previous coatings whether it be paint or powder coat.
Any previous coatings can be removed by blast cleaning; although some coatings can prove to be difficult to remove by blasting alone. If this is the case, then items will be placed in a non-acid dip tank to break down the stubborn coating, and once this is removed, further cleaning will take place before the blast cleaning process.
At this point, your part(s) is ready for blasting. Blasting will clean back to bare metal whilst providing a light texture finish to the part(s) which allows the powder coating to adhere. When blasting, every single area is covered completely and thoroughly with clean media. There are however some areas on parts that should not be blasted: like brake callipers, piston bores or cylinder bores. These areas need to be masked off prior to blasting.
There are many choices for blast cleaning that we are able to offer. Alloy parts, for instance, can be aqua blast cleaned or dry bead blasted, this, however, will depend upon the condition. Other items such as car bodies can be blasted with bead or garnet. In the case of heavy rust, the harsher materials must be utilised to penetrate into deep corrosion.
The coaters nightmare.
At this stage within the process, your part(s) should be as clean as it could possibly be and stripped back to bare metal. This is where we now proceed to the out-gassing procedure. Not all parts, however, need to be out-gassed. Cast iron or cast aluminium is porous, and they can absorb contaminants during the manufacturing process or over the lifetime of the product.
The out-gassing procedure is the process of pre-baking the part(s) in the oven at a higher temperature and a longer time period than the actual powder coat curing procedure. This pre-bake heats up the oils/gasses inside of the part(s) and helps to drive out contaminants. You will often see smoke pouring off during this process; this is the result of oil burning from the porous material. If there is oil/gasses present inside the part(s) and this vital procedure is not carried out, then the contaminants will come out during the powder coat curing which will then most certainly leave little bubbles or bumps in the finish. Unfortunately, sometimes it is impossible to rid all contaminants completely within this process.
There is no set standard for out-gassing as different coaters will follow alternative guidelines. Some will leave the part(s) in the oven until it stops smoking; whilst some will leave it in for a set time. Our procedure is to put the part(s) in the oven at 200 Degrees C. for as long as possible; there is no guarantee however that this will be successful in all cases as some alloys are of poor quality or are mass-produced using cheap base materials leading to prosperity (small bubbles within the casting) when heated. The gas/air within the trapped bubbles expand and push out under the curing powder hence leaving small but very unsightly marks as though it looks like grit under the powder finish.
As mentioned above, besides the cleaning, the blasting process also leaves a textured surface on the part(s), allowing the powder coating to bed into the metal. This texture is responsible for good adhesion and therefore durability of the lifespan of a powder finish. Without this, powder coating can chip or lift relatively easily.
There is an alternative to blasting in order to achieve a good adhesion surface, and this is called phosphate coating; however, these phosphate coatings do not provide as much adhesion as blasting so the durability of the powder coating will not be as effective. Many production powder coating facilities that coat thousands of parts per day will use a phosphate coating instead of blasting. Phosphate coatings are much faster to apply compared to blasting each part individually. Unfortunately, the durability of the powder coating finish suffers because of this. see further details here. https://ctc-powder-coating.co.uk/alloy_powder_coating__outgassing/
After Blast Cleaning.
Blasting will remove almost all contaminates, however, your part(s) will have now become covered in blasting dust. To remove this the part(s) are now handled WITH CLEAN GLOVES, and at this point further de-gassing may be required, if not, then the part(s)are cleaned off with high-pressure dry air and a further clean using a 99% pure alcohol wash.
Masking is dependent on the part(s). Some will require masking before powder coating. As it is the very last step before the powder coat is applied; care is taken to ensure surfaces are as clean as possible, should there be a fingerprint or a speck of dust, this will show up on the finished product. Masking can be a long and arduous task consuming a lot of time. Careful masking is extremely important so as to inhibit the powder from entering areas that should not be coated. The powder, once cured, is one devil of a job to remove.
This is where skill & experience is required. Having the correct machinery and tools for the job is essential. The inexpensive (cheap) or poorly maintained plant will leave a poor and disappointing finish. This is true for the cheap spray guns you see on eBay etc. They do work, but the results are very poor in comparison to the professional machines.
Having a clean and dry air supply is vital, along with the best powder coating guns available. However, you can have all this and more but put into the hands of an inexperienced or slapdash operator then it will all be for nothing.
Materials: (powder), there are many makers producing powders from the cheap and nasty to the expensive and best quality. A great deal of research, science and money has been expended on the best materials; therefore, the better powders are expensive. Cheap powders tend to contain inferior base fillers and are missing vital products within the mix leading to poor finish & disappointing results.
We avoid cheap producers at all costs. Besides suffering from colour fade (as some are not UV stable), powdering and orange peel effect can also be a problem. By using products from high-end producers, all the problems are avoided, and this is the ethos we choose to abide by.
This is the time when all the prep work comes into play—the curing (cross-linking of the powder and the base primer coats). Curing time will very much depend upon the material, weight and size. Base primer coats should be under cured, allowing for the next coat to cross bond for an excellent adhesion so as to give a long and reliable lifespan.
Quality of Work.
Basecoat: (primer)normal procedure. Each and every part(s) has an anti-corrosive coating applied before the top colour coat. There are no short cuts as one coat in our way of thinking is not acceptable or reliable. There are, however, some exceptions and in some cases, depending on the material used there is no requirement for a base coat.
Our strength is knowing that our work is carried out to the best possible standard and to this we offer in 90% of cases our unique five years no quibble anti-corrosion and paint lift warranty. Our clients can rest assured without the need to question the quality and reliability of our work.
To date, in the many years we have been trading, there have only been two occasions where items have come back with corrosion issues, and these were promptly dealt with.
To sum up, quality powder coating is a science and an art form that will outlast other alternatives. There is an extremely wide choice of colours, textures, and clear coats to suit just about any needs of our modern life.
Did you know that powder coating is widely accepted as one of the greenest coatings around? No VOCs or harmful chemicals pumped into the air we all breath during the making or application.
Science. Further reading can be found by following this link.
Hope you have found this short guide useful and should you have any questions please feel free to email or call us.