Abrasive blasting is used widely throughout industry for surface cleaning, finishing, and preparation of a range of materials. These include metals, plastics, wood, and glass. Surfaces can be cleaned far quicker and more effectively than with chemical cleaning to enable the success of further treatment or for cosmetic purposes.
Steels and other metals are used extensively in construction and many manufacturing industries, and need protection from corrosion to preserve structural integrity and extend their life spans. The surfaces of these materials must be meticulously cleaned and prepared for the application of protective coatings. Abrasive blasting has established itself as the preferred method for surface cleaning and preparation for most applications.
What is Abrasive Blasting?
Abrasive blasting is a treatment process whereby an abrasive medium is propelled against a surface at high pressure using blasting nozzles powered by compressed air. This procedure strips the surface clean of dirt, debris, surface coatings and rust, without damaging the underlying material. The process is widely used in industry for a range of applications:
- Surface preparation prior to coating, painting or bonding
- Removing rust, scale or existing coatings
- Removing burrs or edge profiling on machined components
- Finishing of precision parts
- Removing mold flash from plastic components
- Glass etching or frosting
- Providing a cosmetic matte finish on consumer products
The abrasive medium chosen for a particular application depends on the surface finish required. Common blasting abrasives include:
- Steel shot or grit
- Glass bead or crushed glass
- Aluminum oxide
- Silicon carbide
- Coconut or walnut shell
- Copper slag
Traditionally, sand has been used in many applications, but inhaling fine sand during the blasting process poses a serious health risk and can cause silicosis. Consequently, sandblasting operators are required by law to wear protective clothing and equipment in many countries. Nowadays, less harmful abrasives are preferred for blasting applications.
Medium selection for abrasive blasting is critical to the success of the process and media have different properties, including strength, hardness, density, and shape. Most abrasive media are available in a range of particle sizes to suit the surface finish required. Aluminum oxide, in particular, is a tough, hard and durable medium that can be recycled and reused many times. These properties provide aluminum oxide with a significant advantage over many other abrasive media which must be discarded after only a few uses.
What Are the Benefits of Abrasive Blasting?
The primary benefit of abrasive blasting is that the media used are inert, which means that they do not react chemically with the material being cleaned. Alternative methods which use chemical cleaners run the risk of potential reaction and damage to the underlying material. These effects are not always immediately detectable, and problems can become evident long after the surface has been coated. The surface then has to be restripped and recoated, adding to the cost of the process.
Abrasive blasting offers considerable benefits over chemical cleaning for surface preparation:
- Eco-friendliness. Abrasive blasting is far more environmentally friendly than chemical cleaning. The abrasive media themselves are natural, eco-friendly materials that do not emit greenhouse gases during the blasting process.
- Efficiency. Abrasive blasting gets into all the nooks and crannies of any surface undergoing cleaning, ensuring a faster and more thorough process. Chemical cleaning often has to be accompanied by a manual procedure using a scrub brush or scraper, but this process is nowhere near as efficient as abrasive blasting.
- Surface profiling. The adhesion profile of a surface can be controlled by using different particle sizes of the blasting medium for the surface preparation process. The surface profiling, or extent of roughness, depends on the customer’s application requirements for the material. Chemical stripping does not allow any control over the final surface profile.
- Operator safety. Generally, the use of abrasive media for cleaning surfaces is far less of a health risk than chemical cleaning methods. Granted, sandblasting does pose a health risk due to the fine dust and sand particles generated in the process, but operators take protective measures to minimize the danger.
- Effectiveness. Abrasive blasting is not only efficient for surface preparation, but it is also time and cost-effective. State-of-the-art technology also offers mobile solutions for surfaces that are inaccessible to chemical and manual cleaning.
Why is Blasting Important Before Surface Coating?
Generally, abrasive blasting offers an inexpensive way to clean and prepare surfaces, and many abrasive media are reusable. This process also presents economic advantages over traditional methods, cleaning surfaces faster and better while removing undesirable contaminants more efficiently. Any contaminants left on the surface prior to the coating can lead to problems later on. This could call for costly recleaning of the surface or, in extreme cases, could cause failure of the material.
A critical aspect of surface preparation is climate control. Time, temperature and humidity all play a major role in the effectiveness of coating adhesion. Cleaning will expose surfaces like metals to further oxidation, and the threat of corrosion before a coating is applied. It is imperative that coating proceeds as soon as possible after surface preparation. Temperature must be controlled to ensure moisture does not form on the surface. High humidity also increases the risk of moisture condensation on the material surface.
Any condensation on the surface of a metal can cause flash rust before the first coating is applied. This condition will go largely undetected until it becomes a major problem which requires a costly solution. Surface condensation can also result in blistering and delamination of the coating.
It is estimated that up to 80 percent of all premature coating failures are caused by inefficient or inadequate surface preparation. State-of-the-art abrasive blasting technology includes facilities for effective climate control to ensure ideal conditions for surface preparation before coating.
Abrasive blasting is the most efficient and cost-effective method of surface cleaning and preparation for coating. It holds a number of critical advantages over chemical cleaning, including the fact that it can be conducted in a controlled environment. Abrasive blasting, followed by surface coating, ensures the integrity of the underlying material and greatly reduces the need to undergo the costly exercise of recleaning and recoating.
Do you need a reliable abrasive for your blasting application? Contact a leading manufacturer of aluminum oxide blast media to discuss a reliable and cost-effective solution.