SIST EN ISO 12944-4:1998

SLOVENSKI STANDARD
SIST EN ISO 12944-4:1998
01-september-1998
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Paints and varnishes - Corrosion protection of steel structures by protective paint
systems - Part 4: Types of surface and surface preparation (ISO 12944-4:1998)
Beschichtungsstoffe - Korrosionsschutz von Stahlbauten durch Beschichtungssysteme -
Teil 4: Arten von Oberflächen und Oberflächenvorbereitung (ISO 12944-4:1998)
Peintures et vernis - Anticorrosion des structures en acier par systemes de peinture -
Partie 4: Types de surface et de préparation de surfaces (ISO 12944-4:1998)
Ta slovenski standard je istoveten z: EN ISO 12944-4:1998
ICS:
25.220.10 Priprava površine Surface preparation
87.040 Barve in laki Paints and varnishes
91.080.13 Jeklene konstrukcije Steel structures
SIST EN ISO 12944-4:1998 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 12944-4:1998

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SIST EN ISO 12944-4:1998

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SIST EN ISO 12944-4:1998

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SIST EN ISO 12944-4:1998

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SIST EN ISO 12944-4:1998

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SIST EN ISO 12944-4:1998
INTERNATIONAL ISO
STANDARD 12944-4
First edition
1998-05-15
Paints and varnishes — Corrosion
protection of steel structures by protective
paint systems
Part 4:
Types of surface and surface preparation
Peintures et vernis — Anticorrosion des structures en acier par systèmes
de peinture —
Partie 4: Types de surface et de préparation de surface
A
Reference number
ISO 12944-4:1998(E)

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SIST EN ISO 12944-4:1998
ISO 12944-4:1998(E)
Contents Page
1 Scope . 1
2 Normative references . 1
3 Definitions . 3
4 General . 4
5 Types of surface to be prepared . 4
6 Surface preparation methods . 5
7 Surface preparation grades . 9
8 Surface profile (roughness) and surface profile grading . 10
9 Assessment of prepared surfaces . 10
10 Temporary protection of prepared surfaces from corrosion
and/or contamination . 11
11 Preparation of temporarily or partly protected surfaces
before application of further coatings . 11
12 Preparation of hot-dip-galvanized surfaces . 11
13 Preparation of thermally sprayed metal
(zinc and aluminium) surfaces . 12
14 Preparation of zinc-electroplated and sherardized surfaces 12
15 Preparation of other coated surfaces . 12
16 Recommendations regarding pollution and the environment 13
17 Health and safety . 13
Annexes
A Standard preparation grades for primary (overall) surface
preparation . 14
B Standard preparation grades for secondary (partial) surface
preparation . 15
C Procedures for removal of extraneous layers and foreign
matter . 17
©  ISO 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
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SIST EN ISO 12944-4:1998
©
ISO ISO 12944-4:1998(E)
D Bibliography . 19
E Alphabetical index of terms . 20
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SIST EN ISO 12944-4:1998
©
ISO 12944-4:1998(E) ISO
Foreword
ISO (the International Organization for Standardization) is a worldwide
federation of national standards bodies (ISO member bodies). The work of
preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which
a technical committee has been established has the right to be represented
on that committee. International organizations, governmental and non-
governmental, in liaison with ISO, also take part in the work. ISO
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard ISO 12944-4 was prepared by Technical Committee
ISO/TC 35, Paints and varnishes, Subcommittee SC 14, Protective paint
systems for steel structures.
ISO 12944 consists of the following parts, under the general title Paints
and varnishes — Protective paint systems for steel structures:
— Part 1: General introduction
— Part 2: Classification of environments
— Part 3: Design considerations
— Part 4: Types of surface and surface preparation
— Part 5: Protective paint systems
— Part 6: Laboratory performance test methods
— Part 7: Execution and supervision of paint work
— Part 8: Development of specifications for new work and maintenance
Annexes A and B form an integral part of this part of ISO 12944. Annexes
C, D and E are for information only.
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SIST EN ISO 12944-4:1998
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ISO ISO 12944-4:1998(E)
Introduction
Unprotected steel in the atmosphere, in water and in soil is subject to
corrosion that may lead to damage. Therefore, to avoid corrosion damage,
steel structures are normally protected to withstand the corrosion stresses
during the service life required of the structure.
There are different ways of protecting steel structures from corrosion.
ISO 12944 deals with protection by paint systems and covers, in the
various parts, all features that are important in achieving adequate
corrosion protection. Additional or other measures are possible but require
particular agreement between the interested parties.
In order to ensure effective corrosion protection of steel structures, it is
necessary for owners of such structures, planners, consultants, companies
carrying out corrosion protection work, inspectors of protective coatings
and manufacturers of coating materials to have at their disposal state-of-
the-art information in concise form on corrosion protection by paint
systems. Such information has to be as complete as possible,
unambiguous and easily understandable to avoid difficulties and
misunderstandings between the parties concerned with the practical
implementation of protection work.
This International Standard — ISO 12944 — is intended to give this
information in the form of a series of instructions. It is written for those who
have some technical knowledge. It is also assumed that the user of
ISO 12944 is familiar with other relevant International Standards, in
particular those dealing with surface preparation, as well as relevant
national regulations.
Although ISO 12944 does not deal with financial and contractual questions,
attention is drawn to the fact that, because of the considerable implications
of inadequate corrosion protection, non-compliance with requirements and
recommendations given in this standard may result in serious financial
consequences.
ISO 12944-1 defines the overall scope of all parts of ISO 12944. It gives
some basic terms and definitions and a general introduction to the other
parts of ISO 12944. Furthermore, it includes a general statement on health,
safety and environmental protection, and guidelines for using ISO 12944
for a given project.
This part of ISO 12944 describes different types of surface to be protected
and gives information on surface preparation methods such as chemical,
mechanical and flame cleaning. It deals with surface preparation grades,
surface profile (roughness), assessment of prepared surfaces, temporary
protection of prepared surfaces, preparation of temporarily protected
surfaces for further coatings, preparation of existing metal coatings, and
environmental aspects. As far as possible, reference is made to the basic
International Standards on the surface preparation of steel substrates
before application of paints and related products.
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SIST EN ISO 12944-4:1998
©
INTERNATIONAL STANDARD  ISO ISO 12944-4:1998(E)
Paints and varnishes — Corrosion protection of steel structures
by protective paint systems
Part 4:
Types of surface and surface preparation
1  Scope
This part of ISO 12944 deals with the following types of surfaces of steel structures consisting of carbon or low-alloy
steel, and their preparation:
— uncoated surfaces;
— surfaces thermally sprayed with zinc, aluminium or their alloys;
— hot-dip-galvanized surfaces;
— zinc-electroplated surfaces;
— sherardized surfaces;
— surfaces painted with prefabrication primer;
— other painted surfaces.
This part of ISO 12944 defines a number of surface preparation grades but does not specify any requirements for
the condition of the substrate prior to surface preparation.
Highly polished surfaces and work-hardened surfaces are not covered by this part of ISO 12944.
2  Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this part of
ISO 12944. At the time of publication, the editions indicated were valid. All standards are subject to revision, and
parties to agreements based on this part of ISO 12944 are encouraged to investigate the possibility of applying the
most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid
International Standards.
1)
ISO 1461:— , Hot dip galvanized coatings on fabricated ferrous products — Specifications.
ISO 2063:1991, Metallic and other inorganic coatings — Thermal spraying — Zinc, aluminium and their alloys.
ISO 2409:1992, Paints and varnishes — Cross-cut test.

1)  To be published. (Revision of ISO 1459:1973 and ISO 1461:1973)
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ISO 4628-1:1982, Paints and varnishes — Evaluation of degradation of paint coatings — Designation of intensity,
quantity and size of common types of defect — Part 1: General principles and rating schemes.
ISO 4628-2:1982, Paints and varnishes — Evaluation of degradation of paint coatings — Designation of intensity,
quantity and size of common types of defect — Part 2: Designation of degree of blistering.
ISO 4628-3:1982, Paints and varnishes — Evaluation of degradation of paint coatings — Designation of intensity,
quantity and size of common types of defect — Part 3: Designation of degree of rusting.
ISO 4628-4:1982, Paints and varnishes — Evaluation of degradation of paint coatings — Designation of intensity,
quantity and size of common types of defect — Part 4: Designation of degree of cracking.
ISO 4628-5:1982, Paints and varnishes — Evaluation of degradation of paint coatings — Designation of intensity,
quantity and size of common types of defect — Part 5: Designation of degree of flaking.
ISO 4628-6:1990, Paint and varnishes — Evaluation of degradation of paint coatings — Designation of intensity,
quantity and size of common types of defect — Part 6: Rating of degree of chalking by tape method.
ISO 8501-1:1988, Preparation of steel substrates before application of paints and related products — Visual
assessment of surface cleanliness — Part 1: Rust grades and preparation grades of uncoated steel substrates and
steel substrates after overall removal of previous coatings.
Informative Supplement to ISO 8501-1:1988, Representative photographic examples of the change of appearance
imparted to steel when blast-cleaned with different abrasives.
ISO 8501-2:1994, Preparation of steel substrates before application of paints and related products — Visual
assessment of surface cleanliness — Part 2: Preparation grades of previously coated steel substrates after
localized removal of previous coatings.
ISO/TR 8502-1:1991, Preparation of steel substrates before application of paints and related products — Tests for
the assessment of surface cleanliness — Part 1: Field test for soluble iron corrosion products.
ISO 8502-2:1992,
Preparation of steel substrates before application of paints and related products — Tests for the
assessment of surface cleanliness — Part 2: Laboratory determination of chloride on cleaned surfaces.
ISO 8502-3:1992, Preparation of steel substrates before application of paints and related products — Tests for the
assessment of surface cleanliness — Part 3: Assessment of dust on steel surfaces prepared for painting (pressure-
sensitive tape method).
ISO 8502-4:1993, Preparation of steel substrates before application of paints and related products — Tests for the
assessment of surface cleanliness — Part 4: Guidance on the estimation of the probability of condensation prior to
paint application.
ISO 8503-1:1988, Preparation of steel substrates before application of paints and related products — Surface
roughness characteristics of blast-cleaned steel substrates — Part 1: Specifications and definitions for ISO surface
profile comparators for the assessment of abrasive blast-cleaned surfaces.
ISO 8503-2:1988, Preparation of steel substrates before application of paints and related products — Surface
roughness characteristics of blast-cleaned steel substrates — Part 2: Method for the grading of surface profile of
abrasive blast-cleaned steel — Comparator procedure.
ISO 8504-1:1992, Preparation of steel substrates before application of paints and related products — Surface
preparation methods — Part 1: General principles.
ISO 8504-2:1992, Preparation of steel substrates before application of paints and related products — Surface
preparation methods — Part 2: Abrasive blast-cleaning.
ISO 8504-3:1993,
Preparation of steel substrates before application of paints and related products — Surface
preparation methods — Part 3: Hand- and power-tool cleaning.
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ISO 11124-1:1993, Preparation of steel substrates before application of paints and related products —
Specifications for metallic blast-cleaning abrasives — Part 1: General introduction and classification.
ISO 11124-2:1993, Preparation of steel substrates before application of paints and related products —
Specifications for metallic blast-cleaning abrasives — Part 2: Chilled-iron grit.
ISO 11124-3:1993, Preparation of steel substrates before application of paints and related products —
Specifications for metallic blast-cleaning abrasives — Part 3: High-carbon cast-steel shot and grit.
ISO 11124-4:1993, Preparation of steel substrates before application of paints and related products —
Specifications for metallic blast-cleaning abrasives — Part 4: Low-carbon cast-steel shot.
ISO 11126-1:1993, Preparation of steel substrates before application of paints and related products —
Specifications for non-metallic blast-cleaning abrasives — Part 1: General introduction and classification.
ISO 11126-3:1993, Preparation of steel substrates before application of paints and related products —
Specifications for non-metallic blast-cleaning abrasives — Part 3: Copper refinery slag.
ISO 11126-4:1993, Preparation of steel substrates before application of paints and related products —
Specifications for non-metallic blast-cleaning abrasives — Part 4: Coal furnace slag.
ISO 11126-5:1993, Preparation of steel substrates before application of paints and related products —
Specifications for non-metallic blast-cleaning abrasives — Part 5: Nickel refinery slag.
ISO 11126-6:1993, Preparation of steel substrates before application of paints and related products —
Specifications for non-metallic blast-cleaning abrasives — Part 6: Iron furnace slag.
ISO 11126-7:1995, Preparation of steel substrates before application of paints and related products —
Specifications for non-metallic blast-cleaning abrasives — Part 7: Fused aluminium oxide.
ISO 11126-8:1993, Preparation of steel substrates before application of paints and related products —
Specifications for non-metallic blast-cleaning abrasives — Part 8: Olivine sand.
ISO 12944-1:1998, Paints and varnishes — Corrosion protection of steel structures by protective paint systems —
Part 1: General introduction.
EN 10238:1996, Automatically blast-cleaned and automatically prefabrication primed structural steel products.
3  Definitions
For the purposes of this part of ISO 12944, the following definitions apply in addition to those given in ISO 12944-1.
3.1  abrasive blast-cleaning: The impingement of a high-kinetic-energy stream of blast-cleaning abrasive on to
the surface to be prepared.
3.2  blast-cleaning abrasive: A solid material intended to be used for abrasive blast-cleaning. [ISO 11124-1;
ISO 11126-1]
3.3  dust: Loose particulate matter present on a steel surface prepared for painting, arising from blast-cleaning or
other surface preparation processes, or resulting from the action of the environment. [ISO 8502-3]
3.4  dew point: The temperature at which moisture in the air will condense out on to a solid surface. See
ISO 8502-4.
3.5  flash rusting: Slight rust formation on a prepared steel surface soon after preparation.
3.6  grit: Particles that are predominantly angular, that have fractured faces and sharp edges and that are less
than half-round in shape. [ISO 11124-1; ISO 11126-1]
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3.7  mill scale: The heavy oxide layer formed during hot fabrication or heat treatment of steel.
3.8  rust: Visible corrosion products consisting, in the case of ferrous metals, mainly of hydrated iron oxides.
3.9  shot: Particles that are predominantly round, that have a length of less than twice the maximum particle width
and that do not have edges, broken faces or other sharp surface defects. [ISO 11124-1; ISO 11126-1]
3.10  substrate: The surface to which the coating material has been applied or is to be applied. [EN 971-1]
3.11  surface preparation: Any method of preparing a surface for coating.
3.12  white rust: White to dark grey corrosion products on zinc-coated surfaces.
4  General
The primary objective of surface preparation is to ensure the removal of deleterious matter and to obtain a surface
that permits satisfactory adhesion of the priming paint to the steel. It will also assist in reducing the amounts of
contaminants that initiate corrosion.
It is stressed that there is a very wide variation in the condition of steel surfaces requiring cleaning prior to painting.
This particularly applies to maintenance of an already coated structure. The age of the structure and its location, the
quality of the previous surface, the performance of the existing coating system and the extent of breakdown, the
type and severity of previous and future corrosion environments, and the intended new coating system all influence
the amount of preparation required.
When selecting a surface preparation method, it is necessary to consider the preparation grade required to give a
level of surface cleanliness and, if required, a surface profile (roughness) appropriate to the coating system to be
applied to the steel surface. Since the cost of surface preparation is usually in proportion to the level of cleanliness,
a preparation grade appropriate to the purpose and type of coating system or a coating system appropriate to the
preparation grade which can be achieved should be chosen.
Personnel carrying out surface preparation work shall have suitable equipment and sufficient technical knowledge of
the processes involved to enable them to carry out the work in accordance with the required specification. All
relevant health and safety regulations shall be observed. It is important that the surfaces to be treated are readily
accessible and sufficiently illuminated. All surface preparation work shall be properly supervised and inspected.
If the specified preparation grade has not been achieved by the preparation method selected or when the condition
of the prepared surface has subsequently changed before the application of the coating system, relevant parts of
the procedure shall be repeated so as to obtain the specified preparation grade.
Details regarding the preliminary treatment of welds, the removal of weld spatter and removal of burrs and other
sharp edges shall be specified. These measures should normally be taken in connection with the manufacturing
process before the surface preparation.
For further details, see ISO 8504-1.
5  Types of surface to be prepared
The surfaces to be prepared can be divided into the following:
5.1  Uncoated surfaces
Uncoated surfaces consist of bare steel, which may be covered by mill scale or rust and other contaminants. They
shall be assessed in accordance with ISO 8501-1 (rust grades A, B, C and D).
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5.2  Metal-coated surfaces
5.2.1  Thermally sprayed surfaces
Thermally sprayed surfaces consist of steel coated with zinc, aluminium or their alloys by flame or arc spraying in
accordance with ISO 2063.
5.2.2  Hot-dip-galvanized surfaces
Hot-dip-galvanized surfaces consist of steel coated with zinc or zinc alloy by immersion in a molten bath in
accordance with ISO 1461.
5.2.3  Zinc-electroplated surfaces
Zinc-electroplated surfaces consist of steel coated with an electrodeposited zinc coating.
5.2.4  Sherardized surfaces
Sherardized surfaces consist of steel coated with zinc-iron alloy layers obtained by heating the steel component in a
container together with zinc dust.
5.3  Surfaces painted with prefabrication primer
Surfaces painted with prefabrication primer consist of automatically blast-cleaned steel to which a prefabrication
primer has been applied automatically in a plant, in accordance with EN 10238.
NOTE —  For the purposes of this part of ISO 12944, the expression “surfaces painted with prefabrication primer” has a
restricted meaning, in accordance with EN 10238. It is restricted to automatic blast-cleaning and automatic priming.
5.4  Other painted surfaces
Other painted surfaces consist of steel/metal-coated steel that has already been painted .
6  Surface preparation methods
Oil, grease, salts, dirt and similar contaminants shall be removed as far as possible, prior to further surface
preparation, using an appropriate method. In addition, prior removal of heavy, firmly adhering rust and mill scale by
suitable manual or mechanical techniques may be necessary. Where metal-coated steel is to be cleaned, the
technique shall not unnecessarily remove sound metal. A survey of cleaning methods is given in annex C. The
different methods listed are not exhaustive.
6.1  Water, solvent and chemical cleaning
6.1.1  Water cleaning
This method consists in directing a jet of clean, fresh water on to the surface to be cleaned. The water pressure
required depends on the contaminants to be removed such as water-soluble materials, loose rust and poorly
adhering paint coatings. To remove oil, grease, etc., the addition of suitable detergents is necessary. When
detergents have been used in the cleaning operation, rinsing with clean, fresh water is necessary.
6.1.2  Steam cleaning
Steam cleaning is carried out to remove oil and grease. If a detergent is added to the steam, rinsing with clean,
fresh water is necessary.
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6.1.3  Emulsion cleaning
Emulsion cleaning is carried out to remove oil and grease using emulsion cleaners followed by rinsing with clean,
fresh (hot or cold) water.
6.1.4  Alkaline cleaning
Alkaline cleaning is carried out to remove grease or oil by using alkaline cleaners followed by rinsing using clean,
fresh (hot or cold) water.
6.1.5  Organic-solvent cleaning
Organic-solvent cleaning is carried out to remove grease or oil by using suitable organic solvents.
Degreasing with rags impregnated with organic solvent is usually restricted to small areas.
6.1.6  Cleaning by means of chemical conversion
Cleaning by means of chemical conversion (e.g. phosphating, chromating) is used for hot-dip-galvanized surfaces,
electroplated-zinc coatings and sherardized surfaces to give a suitable surface for painting. Otherwise alkaline
solutions or inhibited acids may also be used to prepare the surface. Rinsing with clean, fresh water shall normally
follow. This type of treatment shall only be used with the approval of the manufacturer of the paint system to be
applied.
NOTE —  Treatment by acid or alkaline solutions is known as “mordant wash”.
6.1.7  Stripping
Stripping is the removal of paint coatings by solvent-borne pastes (for coatings soluble in solvents) or alkaline
pastes (for saponifiable coatings). It is normally restricted to small areas. Appropriate subsequent cleaning is
necessary.
6.1.8  Acid pickling
This process involves immersion of the component in a bath containing a suitable inhibited acid which removes mill
scale and rust. The exposed surface shall not be appreciably attacked.
Acid pickling is only suitable for use under carefully monitored factory conditions and is not normally a site process.
6.2  Mechanical cleaning including blast-cleaning
6.2.1  Hand-tool cleaning
Typical hand tools include wire brushes, spatulas, scrapers, synthetic-fabric pads with embedded abrasives, emery
cloth and rust-chipping hammers. For further details see ISO 8504-3.
6.2.2  Power-tool cleaning
Typical power tools include rotating wire brushes, various types of grinder, percussion hammers and needle guns.
Surface areas that cannot be reached with such tools shall be prepared by hand. The cleaning operation shall not
cause any damage or deformation of the structural elements and care shall be taken to avoid the type of surface
damage that chipping tools are liable to cause (notching). When wire brushes are used, it shall be ensured that rust
and contaminants are not merely polished. Polished rust and mill scale can develop a sheen that looks like clean
metal, but which would impair the adhesion of any coating applied to it. Cleaning with power tools is more effective
in terms of area covered and degree of cleanliness than manual surface preparation, but is not nearly as effective
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as blast-cleaning. This should be borne in mind in those cases where power-tool cleaning is preferred to blast-
cleaning (e.g. where the generation of dust or the accumulation of used abrasive is to be avoided). For further
details see ISO 8504-3.
6.2.3  Blast-cleaning
One of the methods specified in ISO 8504-2 shall be used. Blast-cleaning abrasives shall be specified by reference
to the various parts of ISO 11124 and ISO 11126.
6.2.3.1  Dry abrasive blast-cleaning
6.2.3.1.1  Centrifugal abrasive blast-cleaning
Centrifugal abrasive blast-cleaning is carried out in fixed installations or mobile units in which the abrasive is fed to
rotating wheels or impellers positioned to throw the abrasive evenly and at high velocity on to the surfaces to be
cleaned.
For the fields of application, effectiveness and limitations of this technique, see ISO 8504-2.
6.2.3.1.2  Compressed-air abrasive blast-cleaning
Compressed-air abrasive blast-cleaning is carried out by feeding the abrasive into an air stream and directing the
air/abrasive mixture at high velocity from the nozzle on to the surface to be cleaned.
The abrasive may be injected into the air stream from a pressurized container or may be drawn into the air stream
by suction from an unpressurized container.
For the field of application, effectiveness and limitations of this technique, see ISO 8504-2.
6.2.3.1.3  Vacuum or suction-head abrasive blast-cleaning
This method is similar to compressed-air abrasive blast-cleaning (see 6.2.3.1.2) but with the blast nozzle enclosed
in a suction head sealed to the steel surface, collecting the spent abrasive and contaminants. Alternatively, the
air/abrasive stream may be sucked on to the surface by reduced pressure at the suction head.
For the field of application, effectiveness and limitations of this technique, see ISO 8504-2.
6.2.3.2  Moisture-injection abrasive blast-cleaning (compressed-air moisture-injection abrasive blast-clean
...