Legend has it that the sandblasting process was first discovered by American inventor Benjamin Tilman, then an army general, who observed the effect of windblown sand on desert windows. At the time, sand was the most commonly used abrasive, hence the name “sandblasting.” Over the past 50 years, other materials have been used to clean materials.
Today, terms like sandblasting and abrasive blasting more accurately describe the process, as abrasive blasting materials can include any number of products, such as cinders, garnets, glass beads, walnut shells, and corn cobs.
Jim Deardorff, owner of Superior Coatings Sandblasting and Painting in Chillicothe, Mo., says sandblasting can be used on virtually every part of a tractor with the right combination of abrasive material, air pressure, output and nozzles.
Compressor “The air compressor is the most important component in the sandblasting process,” says Deardorff. “It provides the air volume and pressure to move the abrasive through the hose and nozzle at a sufficient speed to remove scale, rust, or old coatings from the target surface.”
For blasting hulls, 3 to 5 cubic feet per minute (cfm) may be sufficient, he said. Larger jobs may require a range of 25 to 250 cfm.
Deardorff explains that when choosing a jet tank or cabinet, there are two types to choose from: suction feed and pressure feed.
Feed System The suction feed system works by drawing the abrasive directly into the gun. This is based on the air supply from the compressor to the gun to create a vacuum. When the gun is triggered, the abrasive is drawn into the gun feed line. The air that comes out then carries the abrasive to the target surface.
“In contrast, a pressure feed system stores the abrasive in a container or reservoir,” he says. “The pressure in the reservoir is the same as the pressure in the material hose. A control valve at the bottom of the reservoir meters the abrasive into a high-velocity air stream. The air stream then delivers the abrasive through the blast hose to the work surface.”
A sandblasting nozzle is a device used to maximize the impact velocity of the sandblasting abrasive. There are many types of nozzles, but four are the most common.
*The straight nozzle creates dense patterns for spot cleaning or blasting a cabinet. It is often used for cleaning small parts.
* Venturi nozzles are the best choice for effective cleaning of large surfaces. However, it is important to note that when blasting at high pressure (100 psi or more), the abrasive can reach speeds of over 500 mph.
*A dual venturi nozzle can be thought of as two nozzles joined end to end. An air inlet in the nozzle body allows the compressor air to mix with the atmosphere. This venturi effect increases the cubic feet per minute and also increases the spray size. Deardorff notes that dual venturi nozzles are the best choice for low-pressure cleaning. This is because the suction effect of the air intake is capable of moving large quantities of heavy, dense abrasive through the material hose at low pressure.
* Fan nozzles are fan-shaped and are used to spray large, flat surfaces. Fan nozzles require more cubic feet of air per minute to operate.
Deardorff says there are also a variety of nozzle liner materials to choose from, including aluminum, tungsten carbide, silicon carbide, and boron carbide. Of course, the choice depends on your budget and the job requirements. Keep in mind that media consumption increases as the nozzles wear.
The abrasive is the actual cleaning part of the sandblasting process. There are four main types of abrasive.
*Natural abrasives include quartz sand, mineral sand, garnet and mirror hematite. They are considered consumable abrasives and are mainly used for outdoor sandblasting.
*Manufactured or manufactured abrasives such as glass beads, aluminum oxide, silicon carbide, steel shot and plastic are reusable and can be used in systems that allow recovery and recycling.
* By-product abrasives (such as cinder, which is a by-product of coal-fired power plants) are considered the most widely used abrasive after quartz sand.
*Non-metallic abrasives are generally classified as organic materials. These include glass beads, plastic materials, and grains such as corn cobs, wheat starch, pecan shells, coconut shells, and walnut shells. Organic abrasives are used when minimal surface damage is desired.
Deardorff notes, “The shape of the abrasive will determine the quality and speed of the sandblasting process. Angled, sharp, or irregularly shaped abrasives clean faster and etch the target surface. Round or spherical abrasives clean the part without removing excess substrate.”
At the same time, hardness affects not only the cleaning speed, but also the amount of dust generated and the decomposition speed, which also directly affects the recycling potential.
The hardness of abrasives is classified on the Mohs scale – from 1 (talc) to 10 (diamond), and the higher the number, the harder the product.
It’s not uncommon to use some sort of middle ground. In fact, Deardorff developed his own a few years ago. Sold under the brand name Classic Blast, it’s a special blend of aluminum oxide, ground black walnut shells, and other materials he mixes himself, including some garnet.
By placing the product in a closed blast tank and using a vacuum to draw the medium into the chamber, he says he can reduce the pressure to 35 pounds while simultaneously cleaning the consumables without causing damage. He often demonstrates the effectiveness of his sandblasting techniques by removing paint from aluminum cans filled with the liquid.
Because the walnut shells in the mixture help remove paint, the metal panels can be polished, and Deardorff said the cleaned surface is also less prone to rust than other types of materials. The walnut shells can also reduce the effects of the more aggressive substances in the mixture.
Post time: Jan-21-2025