Safe Surface Treatment

An abrasive blasting process that combines water with glass bead media is said to provide closed-loop cleaning and surface finishing of a variety of substrates.

The process, developed by Vapormatt Ltd. (Somerset, UK), uses glass abrasive particles as fine as talcum powder. The flow of water holds down dust and eliminates possible buildup of a static charge when using very fine media. According to the company, the water also buffers and lubricates the media particles on impact, allowing production of very fine finishes without damage to the component substrate.

Vapormatt wet blasting is a solvent- and dust-free simultaneous cleaning and degreasing process that employs an operator-safe cleaning solution composed of water, detergent and media. The mixture is delivered through a slurry pump and propelled to the surface through an advanced blast nozzle at variable pressure. The action of the slurry scours the surface to create a thoroughly clean and lightly abraded result without impinging on the metal surface, according to Vapormatt. Effluent is processed through a filtration system, which separates out solid waste for safe disposal and allows recycling of process water.

Typically, no solvents or other potentially hazardous chemicals are used by the wet blast process. However, for tougher soils, the water can be heated and mild detergent added to ensure removal of greases. Vapormatt says biodegradable degreasing compounds can also be added to the mix, facilitating single-step degreasing and superfinishing of parts. Built-in filters remove oil and blast debris in a continuous cycle.

The process is also said to provide a more gentle cleaning action and less potential substrate damage than conventional dry shot blasting.

According to the company, surface defects such as micro-cracks are also more easily identified following wet blasting because the process produces a fine-grained surface. Cleaning continually washes the surface to remove trace elements of caustic materials that can remain in cracks.

The company says the degree of surface cleaning provided can be easily varied by changing the ratio between water pressure and air pressure in the process nozzle. This allows an effective “water buffer” to be maintained between the abrasive media and the surface being processed, creating a lubricating action and washing the surface continuously during processing.

One user of the system is SS Tube Technology Ltd. (Sutton Farm, UK), a manufacturer of race car exhaust systems for teams on the Formula 1, Indy Car, Champ Car, WRC Rally and other race circuits. The exhaust systems are often complex and expensive to fabricate from materials such as Type 321 stainless steel, Inconel or other exotic alloys.

SS Tube Technology installed a Vapormatt wet blast machine as part of a dedicated surface cleaning and preparation cell at the company’s exhaust production and refurbishment facility near Witney, Oxon, UK. The machine, a manual Vapormate 3 with a work envelope measuring 995 × 700 × 700 mm, is used primarily in refurbishment work to thoroughly remove heat scale and other surface contamination from exhaust systems before inspection and rework.

Wet blasting replaced manual cleaning, and has streamlined SS Tube’s refurbishing operation by enabling fast identification of surface imperfections or cracks. The company’s Vapormatt machine is also employed for general component surface preparation and cleaning tasks.