Abrasive blasting is used to remove paint, debris, grease and rust from parts or surfaces, prep surfaces for paints and coatings, increase adhesion of metal and other surfaces and to engrave or etch surfaces. It has grown in popularity over the years because it is safer, more time and cost efficient and provides a superior finish when compared to preparing surfaces using chemical strippers or solvents and manual techniques. However, the greatest advantages will be achieved when the proper media blasting material is selected for a project, as each type of abrasive blast media has distinct characteristics that influence its performance.
This blog will discuss the characteristics, pros and cons and typical applications for several common types of abrasive blasting media and can be used as a guide when selecting material for an abrasive blasting project.
What is Media Blasting?
Media blasting, also called abrasive blasting, is a process that involves propelling an abrasive medium against a surface at high pressure using specialized abrasive blasting equipment and compressed air to strip dirt, debris, coatings or rust from a surface without damaging the material or its substrate.
In the media blasting process, the surface to be cleaned is placed within an abrasive blast cabinet and a technician, who should use protective gear such as gloves, ear protection and a respirator, adds the chosen abrasive blasting media to a blasting machine. Then, using a specialized nozzle that is attached to the blasting machine, the technician uses smooth, side-to-side strokes to “blast” the surface until the desired level of cleanliness is reached for the application.
Abrasive Blasting Media Guide
Although the media blasting process is similar for most applications, the selection of a suitable abrasive blasting media type is critical to ensuring success of the abrasive blasting project. For this reason, it’s important to understand the characteristics of commonly used abrasive blast media.
Here, we will break down abrasive blasting media into hard and soft abrasives. Hard abrasives include aluminum oxide, steel shot and glass beads, which are typically applied to remove paints, coatings, dirt, debris and rust from hard metals and to prep surfaces prior to painting and coating. Soft abrasives include walnut shells, plastic media and soda blast media and find use in removing paints and coatings, dirt, debris and rust from softer metals, as well as soft substrates such as fiberglass, plastics and woods, where etching, marring or pitting are not acceptable.
Hard abrasive blasting media types include:
- Aluminum oxide blast media: Aluminum oxide is a strong, hard abrasive blast media often used for descaling, cleaning, roughening and rust removal, as well as grinding, palling, etching, deburring and cleaning contaminated surfaces. Aluminum oxide blast media is able to cut into almost any type of metal and is used in applications with no special requirements. It is recyclable and can be used in both wet and dry abrasive blasting. Aluminum oxide is one of the most aggressive blasting materials, enabling fast results; however, it may be too aggressive for softer surfaces.
- Steel shot: Available in many sizes and hardness ratings, steel shot blast media can be used for a multitude of surface preparation tasks, including cleaning or stripping unwanted finishes and materials from parts and improving metals to a desired specification. Steel shot is also used in a process called peening, which results in the hardening of the metal’s surface. This abrasive blast media is reusable, recyclable and provides consistent results; however, it should not be used on delicate surfaces. Common applications include cleaning and finishing automotive parts.
- Glass bead blasting abrasives: Made of lead-free, soda-lime type glass in rounded balls, glass beadblasting abrasives provide a satin finishand are suitable for delicate, thin-wall parts. One of the least aggressive “hard media” types, glass bead blasting abrasives can achieve a uniform finish without changing the dimensions of a part. They are used for peening, deburring, removing rust, paint and scale, cosmetic finishing and polishing metals including cast iron, stainless steel and aluminum and for prepping metal surfaces prior to painting or powder coating. Keep in mind that glass bead blasting abrasives will not provide any etch and may take more time than other blasting media.
Soft abrasive blasting media types include:
- Walnut shell media: Among the natural choices, crushed walnut shells provide a softer and milder alternative to hard media blasting options and, as such, are not likely to damage surfaces during the blasting process. Walnut shells can be used in dry blasting applications to strip the topcoat while leaving the undercoat on a surface, which is a time-consuming and delicate process when performed manually. In addition, walnut shells are eco-friendly and reusable, so they are cost efficient. Other applications include improving porosity in ceramics and graffiti removal. Walnut shells, however, are not effective on very hard or thick coatings or other heavy-duty applications.
- Plastic abrasive blast media: Plastic abrasives are used on more delicate surfaces including aluminum, brass, fiberglass and plastics to strip paint and remove contaminants, as well as for deburring and deflashing. Plastic abrasive blast media are essential in the automotive, aerospace and electronics industries where sensitive components cannot have their substrate material modified. Conversely, they will not be effective on hard metals or for finishing applications and they do work slowly.
- Soda blast media: While it’s considered a soft abrasive blasting media, sodium bicarbonate or baking soda, is commonly used in heavy-duty cleaning and blasting applications to remove rust, paint, dirt and corrosion. Soda blast media is inexpensive, eco-friendly and less aggressive than other media, so it is often used to clean delicate, precision components, engine parts and manufacturing equipment. It can be used in both wet and dry blasting applications, but will require enclosures in dry blasting to contain dust and may require a special soda blaster machine rather than traditional blast cabinets.
Because each project has unique specifications, selecting the best abrasive blast media for the application is essential to the success of the job. Close examination of the characteristics and advantages and disadvantages of each type of abrasive blasting media is necessary to determine which one is the most suitable, time effective and cost efficient for the application. For assistance when selecting the blasting media that will provide the optimal surface finish for your next project or to schedule a free media sample test, please contact HTE Technologies, a Tavoron company.
