MontiPower: альтернатива абразивоструйной очистке медным шлаком

Copper slag is a material that is used in various industries for different purposes, and it is one of the most common abrasives in open blasting. This article explains what copper slag is, how copper slag blasting works, what its disadvantages and health risks are, and how a grit-free alternative from MontiPower® compares.

What is copper slag?

To answer this question, we take a look at the copper smelting and refining process. Copper slag is the by-product that separates from the molten copper during smelting. It consists mainly of iron oxides and silica — largely the iron silicate fayalite — with minor amounts of other oxides and trace elements such as zinc, copper and nickel. The molten slag is usually granulated by water (or air) into a hard, glassy granular material.

Although copper slag started out as a waste product, today it is used in many ways. Among other things, it serves as a fill and aggregate material in construction, for example in roads, and as a partial replacement for sand in concrete. One of its best-known uses, however, is as an abrasive for cleaning and preparing surfaces.

What is copper slag blasting?

Abrasive blasting is a widely used technique for preparing, cleaning and machining steel and other metal surfaces. Copper slag is one of the possible abrasives. Other blasting media include sand, glass, plastic and steel grit, and water is used in wet and water-jetting methods; see the 10 types of abrasive blasting compared.

Blasting with copper slag is generally done for two purposes. First, it is an effective way to remove mill scale, rust, dirt, paint and other coatings from metal surfaces. Second, blasting creates a surface profile: the impact of the hard, angular particles leaves an anchor profile that gives a new coating its mechanical key.

How does copper slag blasting work?

In general, blasting with copper slag works in the same way as other dry abrasive blasting techniques. The abrasive is fed into a stream of compressed air and propelled through a nozzle at high velocity against the surface. The force of the impact removes dirt, rust, mill scale, paint and coatings. At the same time, the impact of the angular particles into the metal creates the surface profile that serves as the anchor for the new coating.

Open blasting of this kind needs a compressor, a blast pot, hoses, containment, air-fed respiratory protection for the operator, and collection and disposal of the spent abrasive mixed with the removed coating.

What are the disadvantages and dangers of copper slag blasting?

Blasting with copper slag has been carried out successfully for many years, and copper slag is often chosen as a substitute for silica sand. Over the years, however, its disadvantages and risks have become clearer.

Health risks

• Dust. Slag abrasives break down into fine particles during blasting. According to OSHA, copper slag, like other substitute abrasives, has potential for lung damage, so respiratory protection and dust control are required.
• Trace toxic metals. OSHA notes that slags can contain trace amounts of toxic metals such as arsenic, beryllium and cadmium. These affect not only the operator but can also contribute to pollution of air, soil and water if spent abrasive is not contained.
• The coating being removed. Old coatings may contain lead or hexavalent chromium. Blasting turns them into airborne dust and contaminates the spent abrasive, which then may need to be handled as hazardous waste.

Practical drawbacks

While blasting is very effective for removing dirt and coatings, it is not suitable for every substrate: thin, soft or delicate materials can be damaged if the process is not carefully controlled. Open blasting also requires trained operators, containment and cleanup, which makes it relatively expensive and time-consuming — particularly for small areas, spot repairs and work on operating plants where blasting may not be permitted at all. For a broader overview, see the dangers of sandblasting.

The alternative to copper slag blasting: MontiPower

MontiPower’s Bristle Blaster® is a hand-held, grit-free alternative to blasting with copper slag for steel surface preparation. It removes rust, mill scale and coatings and creates an anchor profile in a single pass, without any loose abrasive. In documented tests on standard steel it reaches cleanliness comparable to ISO 8501-1 Sa 2½ / SSPC-SP 10 with a 65–85 µm Rz anchor profile; results vary with steel grade, rust grade, belt and technique.

For lighter work on car bodies and thin sheet metal, the MBX® removes rust, paint, underseal and sealants without heat or warping. It is a cleaning tool, not a replacement for blasting where a coating-grade profile on structural steel is required.

Because no abrasive such as copper slag is used, there is no blast pot, no media to buy, store or dispose of, and no high-pressure media stream. That removes several of blasting’s largest hazards — but grit-free is not dust-free. The removed rust and coating still become particles, so extraction where appropriate and suitable PPE remain necessary, especially on old coatings that may contain hazardous substances; see surface preparation safety. The tools are designed for single-operator use after basic training, which makes them practical for maintenance crews who would otherwise call in a blasting contractor for small and medium areas. On large, open, new-build areas, abrasive blasting often remains the faster method. More background: the alternative to sandblasting and alternatives to sandblasting steel compared.

How does the alternative to copper slag blasting work?

The Bristle Blaster® is a hand-held tool with a rotating belt of specially designed, patented wire bristles with bent, forward-angled tips. As the belt rotates, the bristle tips strike the so-called accelerator bar, which holds them back for a fraction of a second. When they are released, the tips are launched forward with extra kinetic energy and strike the surface, then rebound.

Because of this high-energy impact, rust, paint, mill scale and coatings are not only removed effectively and precisely, but the tips also leave crater-like micro-indentations — a surface profile comparable in texture to a grit-blasted surface, which serves as the anchor for the new coating. The process is cold-working: no heat is introduced into the substrate.

Copper slag blasting vs Bristle Blaster® at a glance

Frequently asked questions

What is copper slag?

Copper slag is the by-product of copper smelting. It consists mainly of iron oxides and silica, largely as the iron silicate fayalite, with minor amounts of other oxides and trace metals. The molten slag is usually granulated by water or air into a hard, glassy material that is used as blasting abrasive and in construction.

Is copper slag blasting dangerous?

It carries the general hazards of abrasive blasting: high dust levels, noise and a high-pressure media stream. OSHA notes that slags can contain trace amounts of toxic metals such as arsenic, beryllium and cadmium, and that copper slag has potential for lung damage. The removed coating, for example lead paint, adds its own hazard.

What is the alternative to copper slag blasting?

For maintenance, repair and spot work on steel, the Bristle Blaster® is a grit-free alternative: it removes rust, mill scale and coatings and creates a 65–85 µm Rz anchor profile in documented tests, with cleanliness comparable to Sa 2½. For large open new-build areas, abrasive blasting usually remains the faster method.

Does bristle blasting create dust?

It creates far less than abrasive blasting because there is no loose media, but it is not dust-free: the removed rust and coating still become particles. Use extraction where needed and wear suitable PPE, especially when old coatings may contain lead or hexavalent chromium.