If you want powder coating to last longer, you have to put in some very specific prep work, including abrasive blasting. The surface preparation that is required will get rid of flaws and most issues you may face when powder coating.
After cleaning the surface, you’ll want to remove any previous paint or powder coating. You can do this using sandblasting, which is also known as abrasive blasting. In this step, you’ll want to get your surface down as clean as you can to bare metal.
Sometimes, the material you’re powder coating will need to be outgassed to remove oils. Cast aluminium or cast iron surfaces may absorb oils during the process of manufacturing because these materials are porous.
Finally, a second round of sandblasting will provide a texture that the powder coating can anchor to. If you use the right sandblasting medium – note that sand is not the only medium you can use – you’ll get an immaculately clean surface without contaminants. Powder coating specialists swear by sandblasting for the perfect surface prep. Let’s take a look at what the process entails.
Abrasive blastinginvolves firing a stream of abrasive media at high velocities onto a surface to clean, finish and prepare the surface. In the past, this kind of prep work or cleaning was done using more labour-intensive methods.
Manual sanding or wire-brushing were slow processes, especially when you had larger surfaces to clean. Abrasive blasting is great as it speeds up surface prepping by as much as 75%.
Sandblasting is another name for the process, and it has stuck around from time and was used as the blasting medium. These days, health and safety regulations restrict the use of silica sand, beach sand, river sand etc. For sandblasting.
Anything that contains over 1% of fine silica, inhaling, which can cause silicosis, is best avoided. If an operator does use sand, they are required by law to wear protective clothing and equipment, but the rules are different in each state or territory.
How Is It Done?
The blasting is usually done using nozzles powered with compressed air, shooting a stream of material at high velocity. The impact on the surface is so high that it can abrade away paint or contaminants or roughened up surfaces. It can etch glass or metal.
The machine may be manually controlled. Or you can use an automated machine using centrifugal wheels and tumblers. Typically, abrasive blasting is done in closed spaces like blasting cabinets or chambers, but it can also be done at open sites like on boats, bridges, buildings etc.
This process is so versatile that it’s not just your neighbourhood surface treatment company that uses it. Industries working with cement, bricks, concrete and steel use them to clean surfaces. You can also clean plastics, etch glass and sand wood at as large or as precise a scale as you want.
Abrasively cleaning steels and metals used in construction will help to protect the metal against corrosion. This is a vital step to preserve structural integrity and make the structure last longer.
Here are a few common applications of abrasive blasting:
- Removing rust, older coatings, or scale
- Preparing a surface for bonding, painting or powder coating
- Etching or frosting glass
- Finishing precision parts
- Stripping mould flash from plastic parts
- Matt-finishing consumer products for aesthetic appeal
Abrasive Blasting Medium
The type of material or media you use for the sandblasting will depend on what you’re trying to achieve. Common blasting materials used are: sand, garnet, aluminium oxide, steel grit or steel shot, sand, walnut or coconut shells, silicon carbide, plastic and copper slag.
The medium used is vital to the success of the project. You’ll want to consider the shape, density, hardness and strength of the medium, as well as the particle size.
Some materials are superior to others for certain jobs. For instance, aluminium oxide is hard, tough, durable and can be reused many times. Many operators prefer aluminium oxide.
One of the best sandblasting media in the market for abrading and cleaning steel is GMA garnet. It is environmentally friendly, efficient, and safe to use on rust, existing coatings or mill scale.
But every project has different requirements. So, whether you’re doing it yourself or speaking to a surface treatment company, you’ll want to consider what the best medium will be.
Abrasive Blasting Over Chemical Cleaning
Chemical cleaning is the other method of stripping or cleaning surfaces, using organic solvents, commercial cleaners or detergents. These solutions dissolve grease, oil, dirt and other contaminants. The process used may involve steam cleaning, wiping or vapour degreasing.
Chemical cleaning is effective, but abrasive blasting offers several benefits over it-
- Chemicals used may be harmful to the environment, and disposal is difficult. These chemicals are also harsh for the operator. Labour costs can go up due to disposal concerns. Abrasive blasting is a safer, environmentally safer process that’s also more cost-effective, especially when you can reuse and recycle the media you’re using for different jobs.
- Abrasive blasting is efficient because it can get into all the hard-to-reach creases, nooks and crannies of the surface. Unlike chemical cleaning, you don’t need to go over the surface with a scraper or scrub brush afterward.
- Sandblasting lets you control the profile of the surface for better bonding in powder coating or jobs involving spray painting. Different customers may want different roughnesses of the surface. Abrasive blasting gives you that control.
- As long as you’re taking precautions against dust, noise and accidents, abrasive blasting is generally safer for the operator than chemical cleaning. It’s especially important to protect against fine particulate matter on the job. You
- Abrasive blasting is faster and cheaper than chemical cleaning. Modern equipment and tech also offer mobility to help operators reach surfaces that are difficult to clean manually or chemically.
Abrasive blasting is, all in all, one of the best methods of preparing a surface for spray painting services or powder coating. It strips the surface clean of any contaminants that could cause problems later. You won’t have to deal with costly recleaning or material failure.
But the process of stripping a metal clean exposes it to the environment. So controlling the environment on the job is crucial.