Что такое пароабразивная очистка?

This article explains what vapor blasting is, how a vapor blasting machine works, how it compares with dry blasting, its advantages and disadvantages, and when a dry, grit-free power tool is the better choice for preparing steel. For a broader overview of the method, see our vapor blasting hub page.

What is vapor blasting?

Different techniques are used to prepare and clean surfaces, and abrasive blasting is one of the most common. Vapor blasting is similar to other abrasive blasting methods with one important difference: dry abrasive blasting (for example sandblasting) propels abrasive media with air, while vapor blasting adds water to the abrasive. SSPC and NACE refer to the process as wet abrasive blast cleaning (WAB).

The term covers a wide range of equipment. At the gentle end, low-pressure vapor blasting (sometimes called vapor honing) with fine media is used to clean and finish delicate components and to remove light soiling from surfaces such as facades and walls. At the other end, wet abrasive blasting at full blast pressure with angular abrasive removes rust, mill scale and coatings from steel. SSPC and NACE publish wet abrasive blast cleaning standards that mirror the dry grades, from white metal (SSPC-SP 5 (WAB)/NACE WAB-1) and near-white metal (SSPC-SP 10 (WAB)/NACE WAB-2) to brush-off (SSPC-SP 7 (WAB)/NACE WAB-4).

Vapor blasting should not be confused with water jetting, which uses water alone at very high pressure and does not create a primary anchor profile.

How does a vapor blasting machine work?

A vapor blasting machine needs two things: water and an abrasive. The mixture is created in one of three ways: water is injected into a dry abrasive blast stream, abrasive is injected into a pressurized water stream, or a premixed abrasive and water slurry is propelled through the blast hose. Common media include glass beads, aluminum oxide, crushed glass and garnet; silica sand is still used in some places, but respirable crystalline silica is a regulated hazard even when the process is wet.

The pressure can be adjusted. At low pressure, the water film cushions each particle, so the abrasive works more gently and the risk of damaging soft or thin substrates is reduced. This makes low-pressure vapor blasting well suited to more vulnerable surfaces and to removing light contamination.

Vapor blasting vs. dry blasting

The main difference is the water. It has a damping effect on the abrasive, so at the same media and pressure vapor blasting is less aggressive than dry blasting. For heavier contamination, dry blasting is often preferred; for delicate materials, vapor blasting can be a good alternative to sandblasting.

Another major advantage is dust. With dry blasting, the abrasive hits the surface hard, breaks up into fine particles and creates a lot of airborne dust together with the removed coating. In vapor blasting the water wets the particles, so far less dust escapes. The trade-off is that the dust does not disappear: it ends up in the wet slurry, which has to be contained, collected and disposed of, and which may be hazardous if the old coating contains lead or chromates.

Advantages of vapor blasting

• Less airborne dust, which gives a cleaner working environment and better visibility for the operator.
• Gentler action at low pressure, suitable for fragile surfaces, soft metals and precise cleaning of components.
• Cleaning and degreasing in one step: the water helps wash away soluble contamination and light grease.
• Smooth, satin finishes on components when fine media such as glass beads are used.

Disadvantages of vapor blasting

Vapor blasting is well suited to fragile surfaces and precise cleaning, but it has clear disadvantages compared with other methods of surface preparation:

• Flash rust. On carbon steel, rust forms as the water dries. SSPC-VIS 5/NACE VIS 9 shows flash rust grades from none to heavy. It is controlled by drying quickly, adding an inhibitor to the water or spraying inhibitor onto the surface immediately after cleaning; see our guide to flash rust causes and prevention.
• Slurry handling. Water, abrasive and removed coating must be collected, separated and disposed of.
• Drying time. Most coatings must be applied to a dry surface, which adds time between preparation and coating.
• Limited power at low pressure. Heavy rust, mill scale or thick coatings may not be fully removed by low-pressure vapor blasting, and the anchor profile created is small. Steel that needs a coating profile requires higher-pressure wet blasting with angular abrasive, or another method.
• Equipment and containment. Like dry blasting, it needs a compressor or pump, blast equipment and trained operators, which makes it a relatively expensive job for small areas.

What are the alternatives to vapor blasting?

For fragile surfaces, vapor blasting is a good option. For more severe soiling, dry blasting is often preferred. Both, however, share disadvantages: blast equipment, containment and waste handling, and for dry blasting a risk of damaging the substrate. Both are also difficult to carry out yourself, so the work is usually given to a specialist contractor.

For steel that must be cleaned and profiled for a protective coating, MontiPower®'s Bristle Blaster® is a dry, grit-free alternative: a handheld tool that uses no water and no loose abrasive. For thin panels such as vehicle bodywork, the MBX® system removes rust, paint, underseal and sealants without heat or warping. Each tool has its own job; neither replaces blasting everywhere, but on spot repairs, weld seams and in-service assets they remove most of the set-up and clean-up that blasting requires.

More blasting methods are compared in the 10 types of abrasive blasting.

Surface preparation of steel without vapor blasting

Steel surface preparation is governed by standards. Many industrial coating systems for steel require a cleanliness of Sa 2½ (ISO 8501-1), SSPC-SP 10 or NACE No. 2, together with a specified surface roughness. In most cases abrasive grit blasting is used to achieve this. Sandblasting has traditionally been the best-known method, but other abrasives are now more common, partly because of the health risks of silica sand described in the dangers of sandblasting.

The Bristle Blaster® as an alternative to vapor blasting

The patented, grit-free Bristle Blaster® produces a surface quality comparable to grit blasting in both cleanliness and roughness:

• surface cleanliness comparable to Sa 2½ / SSPC-SP 10 (and to Sa 3 / SSPC-SP 5 under suitable conditions)
• an anchor profile of typically 65–85 µm Rz on API 5L steel in documented tests, with up to 120 µm Rz reported

Results vary with steel grade, rust grade, belt and technique, and acceptance is set by the coating specification and the inspector. The main advantages over traditional blasting are simplicity and low set-up cost, because the surface is prepared with a light, handheld machine. Many other small-area alternatives, such as wire brushes and grinders, clean but do not produce a profile suitable for industrial coatings.

Bristle blasting is well suited to portable use: it needs no blast hood with air-fed respiratory equipment, no complex machinery and no media recovery. Standard personal protective equipment for eyes, face, hands and hearing is required, together with respiratory protection, because the removed rust and coating still become dust. Apart from the removed material and worn belts, no additional waste is produced.

How do the alternative tools work?

The Bristle Blaster® is a hand-held tool fitted with a rotating belt of specially shaped, hardened wire bristles. An accelerator bar holds the bristle tips back and releases them so that they strike the surface with kinetic energy comparable to grit-blast media and then immediately rebound. Each strike removes corrosion and leaves a small crater, which gives a texture and visual cleanliness comparable to grit blasting. Because there is no water, there is no process-induced flash rust and no drying time, and the surface can be coated as soon as it has been inspected and cleaned of dust.

Frequently asked questions

Is vapor blasting the same as wet blasting?

Broadly, yes. Both add water to an abrasive stream. The term vapor blasting is often used for lower-pressure work with fine media on delicate or cosmetic parts, while wet abrasive blasting also covers full-pressure blasting of steel to SSPC/NACE wet abrasive blast standards such as SSPC-SP 10 (WAB)/NACE WAB-2.

Does vapor blasting create an anchor profile?

The abrasive, not the water, creates the profile. Low-pressure vapor blasting with fine media cleans and smooths and leaves little profile. Wet abrasive blasting of steel with angular media at higher pressure can produce a profile, which must be measured like any blasted surface, for example with replica tape to ASTM D4417.

Does vapor blasting cause flash rust?

Yes, on carbon steel. Flash rust forms as the water dries, typically within about 30 minutes. SSPC and NACE recognize flash rust grades from none to heavy, and it is controlled by drying the surface quickly, adding an inhibitor to the water or spraying inhibitor on immediately after cleaning. Check that the coating accepts any inhibitor used.

What is a dry, grit-free alternative to vapor blasting for steel?

Bristle blasting. The Bristle Blaster® removes rust and coatings and creates an anchor profile in one pass without water or loose abrasive, so there is no flash rust from the process and no slurry to collect. Documented tests show cleanliness comparable to Sa 2½ / SSPC-SP 10 and 65–85 µm Rz on standard steel.