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ISO
STANDARD
8504-2
First edition
1992-12-01
Preparation of steel Substrates before
application of paints and related
products - Surface preparation
methods -
Part 2:
Abrasive *blast-cleaning
Pr6para tion des subjectiles d ‘acier avant application de peintures et de
produits assimik - M&hodes de preparation des subjectiles -
Partie 2: Dkapage par projection d ’abrasif
Reference number
ISO 8504-2:1992(E)
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ISO 8504-2: 1992(E)
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. Esch 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
(1 EC) 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 8504-2 was prepared by Technical Committee
lSO/TC 35, Paints and varnishes, Sub-Committee SC 12, Preparation of
steel substra tes before application of paints and related products.
ISO 8504 consists of the following Parts, under the general title Prep-
aration of steel Substrates before application of paints and related
products - Surface preparation methods:
- Part 1: General principles
Part 2: Abrasive blas t-cleaning
- Part 3: Hand- and power-tool cleaning
Further Parts are planned.
Annex A of this part of ISO 8504 is for information only.
8 ISO 1992
All rights reserved. NO part of this publication may be reproduced or utilized in any form or
by any means, electronie or mechanical, including photocopying and microfilm, without per-
mission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1 211 Geneve 20 l Switzerland
Printed in Switzerland
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ISO 8504-2: 1992(E)
Introduction
The Performance of protective coatings of paint and related products ap-
plied to steel is significantly affected by the state of the steel surface im-
mediately Prior to painting. The principal factors that are known to
influence this Performance are
a) the presence of rust and mill scale;
b) the presence of surface contaminants, including salts, dust, oils and
greases;
c) the surface Profile.
International Standards ISO 8501, ISO 8502 and ISO 8503 have been
prepared to provide methods of assessing these factors, while ISO 8504
provides guidance on the preparation methods that are available for
cleaning steel Substrates, indicating the capabilities of each in attaining
specified levels of cleanliness.
These International Standards do not contain recommendations for the
protective coating Systems to be applied to the steel surface. Neither do
they contain recommendations for the surface quality requirements for
specific situations even though surface quality tan have a direct influence
on the choice of protective coating to be applied and on its Performance.
Such recommendations are found in other documents such as national
Standards and Codes of practice. lt will be necessary for the users of these
International Standards to ensure that the qualities specified are
- compatible and appropriate both for the environmental conditions to
which the steel will be exposed and for the protective coating System
to be used;
- within the capability of the cleaning procedure specified.
The four International Standards referred to above deal with the following
aspects of preparation of steel Substrates:
ISO 8501 - Visual assessment of surface cleanliness;
ISO 8502 - Tests for the assessment of surface cleanliness;
- Surface roughness characteristics of blast-cleaned steel
ISO 8503
Substrates;
ISO 8504 - Surface prepara tion me thods.
Esch of these International Standards is in turn divided into separate Parts.
The primaty objective of surface preparation is to ensure the removal of
deleterious matter and to obtain a surface that permits satisfactory ad-
. . .
Ill
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ISO 8504-2: 1992(E)
hesion of the priming paint to the steel. lt should also assist in reducing
the amounts of contaminants that initiate corrosion.
This part of ISO 8504 describes abrasive blast-cleaning methods. t should
be read in conjunction with ISO 8504-1.
Abrasive blast-cleaning is a most effective method for mechanica surface
preparation. lt is widely applicable because this method of surface prep-
aration has a number of versatile features listed below.
a) The method allows a high production rate.
b) The equipment tan be stationary or mobile and is adaptable to the
objects to be cleaned.
C) The method is applicable for most types and forms of steel surfaces.
d) Many different surface states tan be produced, for example different
preparation grades and surface profiles.
e) Effects such as cleaning, peening, roughening, levelling and lapping
tan be produced.
f) lt is
possible to remove selectively partly failed coatings leaving Sound
coat ings intact.
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INTERNATIONAL STANDARD
ISO 8504-2: 1992(E)
Preparation of steel Substrates before application of
paints and related products - Surface preparation
methods -
Part 2:
Abrasive blast-cleaning
WARNING - The procedure described in this part of ISO 8504 is intended to be carried out by
qualified chemists or by other suitably trained and/or supervised personnel. The substances and
procedures used in this method may be injurious to health if adequate precautions are not taken.
Attention is drawn in the text to certain specific hazards. This part of ISO 8504 refers only to its
technical suitability and does not absolve the user from statutory obligations relating to health and
safety.
1 Scope 2 Normative references
This part of ISO 8504 describes abrasive blast-
The following Standards contain provisions which,
cleaning methods for the preparation of steel surfaces
through reference in this text, constitute provisions
before coating with paints and related products. lt also
of this part of ISO 8504. At the time of publication, the
contains information on the effectiveness of the indi-
editions indicated were valid. All Standards are subject
vidual methods and their fields of application.
to revision, and Parties to agreements based on this
patt of ISO 8504 are encouraged to investigate the
ISO 8504 is applicable to new and corroded steel
possibility of applying the most recent editions of the
surfaces and to steel surfaces that are uncoated or
Standards indicated below. Members of IEC and ISO
have been previously coated with paints and related
maintain registers of currently valid International
products. For limitations see also note 2.
Standards.
NOTES
ISO 2591-1:1988, Test sieving - Part 1: Methods
using test sieves of woven wire cloth and perfora ted
1 These methods are essentially intended for hot-rolled
me tal pla te.
steel to remove mill scale, rust, etc., but could also be used
for cold-rolled steel of sufficient thickness to withstand the
deformation caused by the impact of abrasive.
ISO 4628-3:1982, Paints and varnishes - Evaluation
of degradation of paint coatings - Designation of in-
2 There are several items that should be included in the
tensity, quantity and size of common types of defect
purchaser ’s procurement documents to Supplement this
- Part 3: Designa tion of degree of rusting.
part of ISO 8504. Items that should be considered as a part
of surface preparation before coating are edge grinding, re-
ISO 8501-1 :1988, Preparation of steel Substrates be-
moval of grease and Oil, porosity of welds, removal of weld
fore application of paints and related products - Vis-
spatter, grinding of welds, filling of pits and other surface
ual assessment of surface cleanliness - Part 1: ßust
imperfections that may Cause premature failure of the
grades and preparation grades of uncoated steel sub-
coating System.
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ISO 850492:1992(E)
NOTE 3 The abrasive is typically propelled either by
strates and of steel Substrates after overall removal
centrifugal forte or by a high-velocity stream of fluid such
of previous coatings.
as air or water to remove rust, mill scale, existing coatings
and other contaminants and expose the Substrate. The
ISO 8501-2: -l), Preparation of steel Substrates before
cleaned surface has a characteristic secondary Profile de-
application of paints and related products - Visuai
pendent on the blast-cleaning conditions, the properties of
assessment of surface cleanliness - Part 2: Prep-
the abrasive, the initial condition of the surface and the
aration grades of previously coated steel Substrates
properties of the steel being blast-cleaned. The initial sur-
after localized removal of previous coatings.
face roughness or primary Profile may be altered by the
abrasive blast-cleaning procedure. Surface profiles are as-
sessed using the method described in ISO 85032. When
ISO/TR 8502-1 :1991, Preparation of steel Substrates
selecting a surface preparation method, it is necessary to
before application of paints and related products -
consider the preparation grade required to give a level of
Tests for the assessment of surface cleanliness -
sut-face cleanliness and, if required, a surface Profile
Part 1: Field test for soluble iron corrosion products.
(roughness), such as coarse, medium or fine (see
ISO 8503-1 and ISO 8503~Z), appropriate to the coating
ISO 8502-27 992, Preparation of steel Substrates be-
System to be applied to the steel surface. Since the tost
fore application of paints and related products -
of surface preparation is usually in Proportion to the level
Tests for the assessment of surface cleanliness -
of cleanliness, a preparation grade appropriate to the pur-
Part 2: Laboratory determination of chloride on
pose and type sf coating System or a coating System ap-
cleaned surfaces. propriate to the preparation grade which tan be achieved
should be Chosen.
ISO 8502-37 992, Preparation of steel Substrates be-
fore application of pain ts and related products -
Tests for the assessment of surface cleanliness -
Part 3: Assessment of dust on steel surfaces pre-
pared for pain ting (pressure-sensitive tape me thod).
4 Abrasives
ISO 8503-1 :1988, Preparation of steel Substrates be-
fore applica tion o f paints and rela ted products - Sur-
face roughness characteristics of blast-cleaned steel
4.1 Materials and types
Substrates - Part 1: Specifications and definitions for
ISO surface Profile comparators for the assessment
of abrasive blast-cleaned surfaces.
4.1.1 A wide variety of natura1 and synthetic solid
materials and several liquids are used for abrasive
ISO 8503-2:1988, Preparation of steel Substrates be-
blast-cleaning. Solid materials commonly in use for
fore applica tion of paints and related products - Sur-
the preparation of steel surfaces before coating are
face roughness characteristics of blast-cleaned steel
given in table 1. Esch material provides a character-
Substrates - Part 2: Method for the grading of sur-
istic Performance and surface finish.
face Profile of abrasive blast-cleaned steel -
When selecting a blast-cleaning abrasive, the follow-
Compara tor procedure.
ing factors relating to its initial condition shall be con-
ISO 8504-1 :1992, Preparation of steel Substrates be- sidered:
fore application of paints and related products - Sur-
face preparation methods - Part 1: General - sub-group and type (see table 1);
principles.
- indication of Chemical composition;
ISO 8504-3: -l), Preparation of steel Substrates before
application of paints and related products - Surface - range of particle size (see 4.1.2);
preparation methods - Part 3: Hand- and power-tool
cleaning. - particle hardness (for example Vickers, Rockwell
or Mohs, or as measured by another appropriate
method).
3 Definition
For the purposes of this part of ISO 8504, the follow-
ing definition applies.
4.1.2 The size and shape of the particles of an
31 . abrasive blast-cleaning: The impingement of a abrasive may Change during use or re-use and this
high-kin etic-energy stream of abrasive on to the sur- Change tan affect the resultant surface texture of the
be prepared.
face to blast-cleaned steel.
1) To be published.
2
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ISO 8504-2: 1992(E)
Table 1 - Commonly used blast-cleaning abrasives for steel Substrate preparation
Initial particle
Com-
shape
Abbreviation Remarks
TYPe
parat00
(see table 2)
Metallic (M)
Mainly for
blast-cleaning compressed-
Cast iron Chilled M/CI G
G
abrasives air blast-
cleaning
High-carbon
M/HCS S or G 9)
Cast steel
Mainly for
Low-carbon S
M/LCS S
centrifugal
blast-cleaning
Cut steel
M/CW C 9)
wire
Non-metallic (N) Natura1 Silica sand N/SI
blast-cleaning
G
G
abrasives Mainly for
Olivine sand N/OL
compressed-
air blast-
G
Staurolite N/ST S
cleaning
Garnet N/GA G G
Synthetic (Calcium
Iron fur-
silicate NIFE
nace slag
slags)
Copper re-
N/CU
Mainly for
finery slag
(Ferrous
compressed-
silicate G G
air blast-
slags)
Nickel re-
cleaning
N/NI
f inery slag
(Aluminium
Coal fur-
silicate N/CS
nace slag
slags)
Fused aluminium Oxide N/FA G G
1) Comparator to be used when assessing the resultant surface Profile. The method for evaluating the surface Profile b
comparator is described in ISO 85032.
2) Certain types of abrasive rapidly Change their shape when used. As soon as this happens, the appearance of the surfac
Profile changes and becomes closer to that of the “shot” comparator.
Table 2 - Initial particle shape
Designation and initial particle shape Symbol
Shot - round S
Grit - angular, irregular G
l
Cylindrical - sharp-edged C
I
3
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ISO 8504-2: 1992(E)
4.3.3 When selecting an abrasive, it is essential that
4.2 General requirements
the following considerations are taken into account:
a) The influence sf a particular particle size on the
4.2.1 Technical
resulting surface Profile is normally greater for
metallic abrasives than for non-metallic abrasives.
Abrasives shall be dry (except when added to press-
This is because the shatter characteristics differ
urized liquid or slurry blast-cleaning Systems) and shall
and because differentes in density affect the
be free-flowing to permit consistent metering into the
kinetic energy of the abrasive particles.
blast stream.
) A balanced mixture of particle sizes will produce
Abrasives shall be free from corrosive constituents
the Optimum level of cleanliness, cleaning rate and
and adhesion-impairing contaminants. Because of
surface Profile.
their deleterious effect on the blast-cleaned steel
surface, permanently contaminated abrasives (for ex-
In blas t-cleaning plants where the abrasive is re-
ample those that cannot be cleaned before recycling
cycled, it is nece ssary
and abrasives produced from slag that has been
granulated by the use of Saline water, i.e. sea water,
- to remove dust and contaminants before the
for cooling) are not permitted.
abrasive is re-used and
- to make up for the abrasive which is lost by
4.2.2 Health and safety
wear and adherence to the workpieces. This is
done by controlled additions of new abrasive
Equipment, materials and abrasives used for surface
so that the abrasive mixture is maintained
preparation tan be hazardous if used carelessly. Many
within the prescribed particle size limits or par-
national regulations exist for those materials and
title size distribution.
abrasives that are considered to be hazardous during
or after use (waste management), such as free silica
Complete renewal of abrasive charges in recycling
or carcinogenic or toxic substances. These regulations
machines requires a period of use before the mixture
are therefore to be observed. lt is important to ensure
reaches a steady condition.
that adequate instructions are given and that all re-
quired precautions are exercised.
5 Abrasive blast-cleaning methods
4.3 Selection considerations
5.1 Dry abrasive blast-cleaning
4.3.1 Selection of a suitable abrasive, together with
an appropriate blast-cleaning method and operating
5.1 .l Centrifugal abrasive blast-cleaning
conditions, is necessary to achieve the required stan-
dard of surface preparation.
5.1 .l .l Principle
The type of blast-cleaning abrasive - i.e. its particle
size distribution, shape, hardness, density and impact
Centrifugal abrasive blast-cleaning is carried out in
behaviour (deformation or shatter characteristics) - enclosed plants in which the abrasive is fed to rotating
is important in determining the Standards of cleanli-
wheels or impellers positioned to throw the abrasive
ness, the cleaning rate and the resulting surface pro-
evenly and at high velocity on to the surfaces t
...