ISO 8501-1:2007

IMPORTANT — The ref-
INTERNATIONAL
ISO
erence photographs util-
STANDARD
ized for the assessment
8501-1
of steel surfaces when
using this part of
NORME
Second edition
ISO 8501 are not in-
Deuxième édition
cluded in this electronic
INTERNATIONALE
2007-05-01
file because the quality
of their reproduction is
subject to change when
they are viewed on
screen or printed out. It
Preparation of steel substrates before
is important that only the
application of paints and related products —
photographs contained
Visual assessment of surface cleanliness —
in officially printed
Part 1:
versions of this part
of ISO 8501, purchased Rust grades and preparation grades of uncoated

from ISO or from ISO steel substrates and of steel substrates after
member bodies or their
overall removal of previous coatings
distributors, are used
when carrying out as-
Préparation des subjectiles d'acier avant
sessments.
application de peintures et de produits
assimilés — Évaluation visuelle de la propreté
IMPORTANT — Les cli-
d'un subjectile —
chés photographiques
représentatifs servant à
Partie 1:
l'évaluation visuelle des
Degrés de rouille et degrés de préparation
subjectiles en acier à
des subjectiles d'acier non recouverts et
l'aide de la présente par-
des subjectiles d'acier après décapage sur toute
tie de l'ISO 8501 ne sont
la surface des revêtements précédents
pas inclus dans le pré-
sent fichier électronique
parce que la qualité de
leur reproduction ne
peut être garantie lors-
qu'ils sont affichés à
l'écran ou imprimés. Il
est important que seuls
les clichés photogra-
phiques contenus dans
les versions officielles
de la présente partie
de l'ISO 8501, achetées
auprès de l'ISO, des
comités membres de
Reference number
Numéro de référence
l'ISO ou de leurs distri-
buteurs, soient utilisés
©
lors de s évaluations.  ISO and SIS 2007/ISO et SIS 2007

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© ISO and SIS 2007 – All rights reserved
ii
© ISO et SIS 2007 – Tous droits réservés

Page
English text .1
Texte français .23
Deutscher Text.45
Svensk text.69
Photographs / Photographies / Photographische Vergleichsmuster /
Fotografier
© ISO and SIS 2007 – All rights reserved
iii
© ISO et SIS 2007 – Tous droits réservés

Contents Page
Foreword .2
Introduction.4
1 Scope.7
2 Rust grades.8
3 Preparation grades.9
4 Procedure for visual assessment of steel substrates.12
5 Photographs .13
Annex A (informative) Representative photographic examples
of the change of appearance imparted to steel when
blast-cleaned with different abrasives .15
Bibliography.19

© ISO and SIS 2007 – All rights reserved 1

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.
International Standards are drafted in accordance with the rules given in
the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International
Standards. 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.
Attention is drawn to the possibility that some of the elements of this
document may be the subject of patent rights. ISO shall not be held
responsible for identifying any or all such patent rights.
ISO 8501-1 was prepared by Technical Committee ISO/TC 35, Paints and
varnishes, Subcommittee SC 12, Preparation of steel substrates before
application of paints and related products.
This second edition cancels and replaces the first edition
(ISO 8501-1:1988). The main change is that the Informative Supplement
ISO 8501-1:1988/Suppl.1994 has been included as Annex A.
2 © ISO and SIS 2007 – All rights reserved

ISO 8501 consists of the following parts, under the general title 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 of steel substrates after overall removal of previous
coatings
⎯ Part 2: Preparation grades of previously coated steel substrates after
localized removal of previous coatings
⎯ Part 3: Preparation grades of welds, edges and other areas with
surface imperfections
⎯ Part 4: Initial surface conditions, preparation grades and flash rust
grades in connection with high-pressure water jetting

© ISO and SIS 2007 – All rights reserved 3

Introduction
The performance of protective coatings of paint and related products
applied to steel is significantly affected by the state of the steel surface
immediately 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 can have a direct influence
on the choice of protective coating to be applied and on its performance.
Such recommendations are given in other documents such as national
standards and codes of practice. It 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.
4 © ISO and SIS 2007 – All rights reserved

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;
ISO 8503 — Surface roughness characteristics of blast-cleaned steel
substrates;
ISO 8504 — Surface preparation methods.
Each of these International Standards is in turn divided into separate parts.
This part of ISO 8501 identifies four levels (designated as “rust grades”) of
mill scale and rust that are commonly found on surfaces of uncoated
erected steel and steel held in stock. It also identifies certain degrees of
visual cleanliness (designated as “preparation grades”) after surface
preparation of uncoated steel surfaces and of steel surfaces after overall
removal of any previous coating. These levels of visual cleanliness are
related to the common methods of surface cleaning that are used prior to
painting.
This part of ISO 8501 is intended to be a tool for visual assessment of
rust grades and of preparation grades. It includes 28 representative
photographic examples.
Fourteen of these photographic examples show steel surfaces that have
been subjected to dry blast-cleaning using quartz sand as the abrasive.
The use of other abrasives may affect the appearance of the surface.
Colour changes caused by different abrasives are shown in Annex A.
NOTE Twenty-four of the photographs originated from the Swedish standard
SIS 05 59 00-1967, Pictorial surface preparation standards for painting steel
surfaces. The other four photographs originated from the German standard
DIN 55 928, Part 4, Supplement 1 (August 1978), Protection of steel structures from
corrosion by organic and metallic coatings; preparation and testing of surfaces;
photographic standards.
© ISO and SIS 2007 – All rights reserved 5

INTERNATIONAL STANDARD ISO 8501-1:2007(E)

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 of steel substrates after
overall removal of previous coatings
1 Scope
This part of ISO 8501 specifies a series of rust grades and preparation
grades of steel surfaces (see Clauses 2 and 3, respectively). The various
grades are defined by written descriptions together with photographs that
are representative examples within the tolerance for each grade as
described in words.
It is applicable to hot-rolled steel surfaces prepared for painting by methods
such as blast-cleaning, hand and power tool cleaning and flame cleaning,
although these methods rarely lead to comparable results. Essentially,
these methods are intended for hot-rolled steel, but blast-cleaning methods,
in particular, could also be used on cold-rolled steel of sufficient thickness
to withstand any deformation caused by the impact of the abrasive or the
effects of power tool cleaning.
This part of ISO 8501 is applicable also to steel substrates that show
residues of firmly adhering paint and other foreign matter (see Note 2 to 3.1)
in addition to residual mill scale.
© ISO and SIS 2007 – All rights reserved 7

NOTE 1 The preparation grades of previously painted steel surfaces after only
[1]
localized removal of paint coatings form the subject of ISO 8501-2 .
This part of ISO 8501 relates the cleanliness of the surface to its visual
appearance. In many instances, this is sufficient for the purpose but for
coatings likely to be exposed to severe environments, such as water
immersion and continuous condensation conditions, consideration should
be given to testing for soluble salts and other invisible contaminants on
the visually clean surface by the physical and chemical methods which
[2]
form the subjects of the various parts of ISO 8502 . The roughness
characteristics of the surface should also be considered by reference to the
[3]
various parts of ISO 8503 .
NOTE 2 This part of ISO 8501 contains the text in two of the three official
languages of ISO, English and French. It also contains the text in German,
published under the responsibility of DIN, and the text in Swedish, published under
the responsibility of SIS.
2 Rust grades
Four rust grades, designated A, B, C and D respectively, are specified. The
rust grades are defined by written descriptions.
A Steel surface largely covered with adhering mill scale but little, if any,
rust.
B Steel surface which has begun to rust and from which the mill scale
has begun to flake.
C Steel surface on which the mill scale has rusted away or from which it
can be scraped, but with slight pitting visible under normal vision.
D Steel surface on which the mill scale has rusted away and on which
general pitting is visible under normal vision.
Representative photographic examples of these rust grades are appended
to this part of ISO 8501 (see Clause 5 for details).
8 © ISO and SIS 2007 – All rights reserved

3 Preparation grades
3.1 General
A number of preparation grades, indicating the method of surface
preparation and the degree of cleaning, are specified. The preparation
grades are defined in 3.2, 3.3 and 3.4 by written descriptions of the surface
appearance after the cleaning operation. Representative photographic
examples of these preparation grades are appended to this part of
ISO 8501 (see Clause 5 for details).
Each preparation grade is designated by the appropriate letters “Sa”, “St”
or “FI” to indicate the type of cleaning method used. The number following,
if any, indicates the degree of cleaning from mill scale, rust and previous
coatings.
The photographs are designated by the original rust grade before cleaning
and the designation of the preparation grade, for example B Sa 2½.
NOTE 1 The term “foreign matter” used in 3.2, 3.3 and 3.4 may include water-
soluble salts and welding residues. These contaminants cannot be completely
removed from the surface by dry blast-cleaning, hand and power tool cleaning or
flame cleaning; wet blast-cleaning or water jetting should be used.
NOTE 2 Mill scale, rust or a paint coating is considered to be poorly adhering if it
can be removed by lifting with a blunt putty knife.
3.2 Blast-cleaning, Sa
Surface preparation by blast-cleaning is designated by the letters “Sa”.
Descriptions of the blast-cleaning grades are given in Table 1.
Prior to blast-cleaning, any heavy layers of rust shall be removed by
chipping. Visible oil, grease and dirt shall also be removed.
After blast-cleaning, the surface shall be cleaned from loose dust and
debris.
© ISO and SIS 2007 – All rights reserved 9

NOTE Descriptions of surface preparation methods by blast-cleaning,
including treatment prior to, and after, the blast-cleaning procedure, are given in
[4]
ISO 8504-2 .
Table 1 — Blast-cleaning grades
Sa 1 Light blast- When viewed without magnification, the surface shall
cleaning be free from visible oil, grease and dirt, and from poorly
adhering mill scale, rust, paint coatings and foreign
matter (see Note 1 to 3.1). See photographs B Sa 1,
C Sa 1 and D Sa 1.
Sa 2 Thorough blast- When viewed without magnification, the surface shall
cleaning be free from visible oil, grease and dirt, and from most
of the mill scale, rust, paint coatings and foreign
matter. Any residual contamination shall be firmly
adhering (see Note 2 to 3.1). See photographs B Sa 2,
C Sa 2 and D Sa 2.
Sa 2½ Very thorough When viewed without magnification, the surface shall
blast-cleaning be free from visible oil, grease and dirt, and from mill
scale, rust, paint coatings and foreign matter. Any
remaining traces of contamination shall show only
as slight stains in the form of spots or stripes. See
photographs A Sa 2½, B Sa 2½, C Sa 2½ and
D Sa 2½.
Sa 3 Blast-cleaning When viewed without magnification, the surface shall
to visually clean be free from visible oil, grease and dirt, and shall be
steel free from mill scale, rust, paint coatings and foreign
matter. It shall have a uniform metallic colour. See
photographs A Sa 3, B Sa 3, C Sa 3 and D Sa 3.
3.3 Hand and power tool cleaning, St
Surface preparation by hand and power tool cleaning, such as scraping,
wire-brushing, machine-brushing and grinding, is designated by the
letters “St”. Descriptions of the hand and power tool cleaning grades are
given in Table 2.
Prior to hand and power tool cleaning, any heavy layers of rust shall be
removed by chipping. Visible oil, grease and dirt shall also be removed.
10 © ISO and SIS 2007 – All rights reserved

After hand and power tool cleaning, the surface shall be cleaned from loose
dust and debris.
NOTE 1 Descriptions of surface preparation methods by hand and power tool
cleaning, including treatment prior to, and after, the hand and power tool cleaning
[5]
procedure, are given in ISO 8504-3 .
NOTE 2 Preparation grade St 1 is not included, as it would correspond to a
surface unsuitable for painting.
Table 2 — Hand and power tool cleaning grades
St 2 Thorough hand When viewed without magnification, the surface shall
and power tool be free from visible oil, grease and dirt, and from poorly
cleaning adhering mill scale, rust, paint coatings and foreign
matter (see Note 1 to 3.1). See photographs B St 2,
C St 2 and D St 2.
St 3 Very thorough As for St 2, but the surface shall be treated much
hand and power more thoroughly to give a metallic sheen arising from
tool cleaning the metallic substrate. See photographs B St 3, C St 3
and D St 3.
3.4 Flame cleaning, FI
Surface preparation by flame cleaning is designated by the letters “FI”.
Descriptions of the flame cleaning grades are given in Table 3.
Prior to flame cleaning, any heavy layers of rust shall be removed by
chipping.
After flame cleaning, the surface shall be cleaned by power tool wire-
brushing.
NOTE Flame cleaning includes final power tool wire-brushing to remove the
products of the cleaning process; hand wire-brushing does not achieve a
satisfactory surface for painting.
© ISO and SIS 2007 – All rights reserved 11

Table 3 — Flame cleaning
FI Flame cleaning When viewed without magnification, the surface shall
be free from mill scale, rust, paint coatings and
foreign matter (see Note 1 to 3.1). Any remaining
residues shall show only as a discoloration of the
surface (shades of different colours). See
photographs A FI, B FI, C FI and D FI.
4 Procedure for visual assessment of steel substrates
Either in good diffuse daylight or in equivalent artificial illumination,
examine the steel surface and compare it with each of the photographs
appended to this part of ISO 8501 (see Clause 5 for details), using normal
vision. Place the appropriate photograph close to, and in the plane of, the
steel surface to be assessed.
For rust grades, record the assessment as the worst grade that is evident.
For preparation grades, record the assessment as that grade nearest in
appearance to that of the steel surface.
NOTE 1 In addition to the type of cleaning method used, for example dry blast-
cleaning using a particular type of abrasive, the following factors can influence the
result of the visual assessment:
a) initial state of the steel surface other than any of the standard rust grades A, B,
C and D;
b) colour of the steel itself;
c) regions of differing roughness, resulting from differential corrosion attack or
uneven removal of material;
d) surface irregularities such as dents;
e) marks from tools;
f) uneven lighting;
g) shadowing of the surface profile caused by angled projection of abrasive;
h) embedded abrasives.
12 © ISO and SIS 2007 – All rights reserved

NOTE 2 For previously painted surfaces that have been prepared for renewed
painting, only photographs with rust grade designations D or C (for example:
D Sa 2½ or C Sa 2½) may be used for the visual assessment. The choice (for
example between D Sa 2½ and C Sa 2½) depends on the degree of pitting.
5 Photographs
Twenty-eight representative photographic examples for comparison with
steel substrates are appended.
These photographs are shown full size, i.e. not magnified. For convenience
in use, they are displayed in the order shown in Figures 1 and 2.
Four photographs relate specifically to the rust grades A, B, C and D (see
Clause 2).
Twenty-four photographs, A Sa 2½ to D FI, relate specifically to the
preparation grades obtained by dry blast-cleaning, by hand and power tool
cleaning, and by flame cleaning (see Clause 3). Other methods, such as
wet blast-cleaning and water jetting, produce surfaces that may differ in
appearance, colour, etc., but the photographs can still be used to give an
indication of the preparation grade.
Fourteen photographs, A Sa 2½ to D Sa 3, show steel surfaces that have
been subjected to dry blast-cleaning with abrasives containing quartz sand.
The use of such abrasives in enclosed areas is prohibited in many
countries except under strictly controlled conditions. Therefore abrasives of
other types (and hence colour) are often used for dry blast-cleaning. These
abrasives may produce a different surface appearance, even after
meticulous cleaning of the blast-cleaned surface (see Annex A).
There are no photographs representing A Sa 1, A Sa 2, A St 2 or A St 3
because these preparation grades are not achievable and the existing
photographs are sufficiently indicative.
© ISO and SIS 2007 – All rights reserved 13

Figure 1 — Layout and sequence of the appended representative
photographic examples for rust grades

a)  Blast-cleaning
b)  Hand and power tool cleaning

c)  Flame cleaning
Figure 2 — Layout and sequence of the appended representative
photographic examples for preparation grades
14 © ISO and SIS 2007 – All rights reserved

Annex A
(informative)
Representative photographic examples
of the change of appearance imparted to steel
when blast-cleaned with different abrasives
A.1 General
This part of ISO 8501 provides written specifications and representative
photographic examples of a number of rust grades and preparation grades.
Fourteen of these photographic examples, A Sa 2½ to D Sa 3, show steel
surfaces that have been subjected to dry blast-cleaning with abrasives
containing quartz sand.
The basis of this annex is that many different abrasives are used for blast-
cleaning. Since some abrasive remains embedded in a blast-cleaned
surface, the colour of the abrasive affects the appearance of the surface.
Generally, the use of dark-coloured abrasives, such as copper refinery or
coal furnace slags, will result in an overall darker, duller appearance than if
sand is used. Some hard, metallic abrasives, although themselves not
coloured black, will also create a darker appearance due to the shadows
formed by the deep-sided pitting on the blast-cleaned surface.
In addition, the use of quartz sand as an abrasive is subject to a number of
prohibitive regulations in many countries and its use for the photographic
representations in this part of ISO 8501 should not be taken as general
approval for its use.
This annex provides representative photographic examples of mild steel of
rust grade C, blast-cleaned to preparation grade Sa 3, using six different
(metallic and non-metallic) abrasives that are in common use. For
comparison, a photographic representation of the original steel surface, i.e.
the surface before preparation, is also included.
© ISO and SIS 2007 – All rights reserved 15

A.2 Procedure for visual assessment of steel substrates
Assess the preparation grade and record the result of the assessment as
described in Clause 4.
If the appearance of the surface being assessed is different from that in the
nearest photograph, use the examples described in this annex and shown
in the photograph at the very end of this part of ISO 8501 as a guide to the
change in colour depth and tone that may be due to the abrasive used to
prepare the surface.
The examples illustrated in this annex meet the written description of
preparation grade Sa 3 (see Table 1).
In all cases, assess compliance against the written descriptions for the
preparation grades given in Table 1.
A.3 Photographic examples
Six representative photographic examples are shown at the very end of this
part of ISO 8501. The examples are shown full size, i.e. not magnified.
These examples have been prepared by blast-cleaning mild steel of rust
grade C to preparation grade Sa 3, as specified in Table 1, with six different
abrasives that are in common use. Part of the original steel surface is
included for visual comparison purposes. The photographic examples are
displayed in the order shown in Figure A.1.
The abrasives were chosen to provide a “Medium” surface profile as
described in ISO 8503-2. The photograph was obtained by progressively
masking a single mild-steel plate into strips and blast-cleaning the rust
grade C surface thus exposed with a different abrasive for each strip to
preparation grade Sa 3. Care was taken to protect previously prepared
strips when blast-cleaning other strips. The plate was photographed shortly
after completion of the blast-cleaning in order to avoid deterioration of the
freshly prepared surfaces.
16 © ISO and SIS 2007 – All rights reserved

The photograph illustrates the differences in surface appearance, including
colour, that are obtained when the same substrate is prepared by blast-
cleaning with different abrasive materials to the same preparation grade.
The photograph illustrates the surface appearance typically obtained using
each abrasive under the conditions described above but it should be noted
that variations may be obtained in practice.
The high-carbon cast-steel shot abrasive used was of grade S 100 as
[7]
specified in ISO 11124-3 . The chilled-iron grit abrasive was in accordance
[6]
with grade G 070 of ISO 11124-2 . The two steel grit abrasives were in
accordance with grade G 070 of ISO 11124-3. Their hardnesses, determined
[8]
by the method described in ISO 11125-3 , are stated in the captions to
the relevant parts of the photograph. Copper refinery slag and coal furnace
[9] [10]
slag abrasives are specified in ISO 11126-3 and ISO 11126-4
respectively.
© ISO and SIS 2007 – All rights reserved 17

Original mild-steel plate
Rust grade C
High-carbon cast-steel shot
Grade S 100
Vickers hardness 390 HV to 530 HV
Steel grit
Grade G 070
Vickers hardness 390 HV to 530 HV
Steel grit
Grade G 070
Vickers hardness 700 HV to 950 HV
Chilled-iron grit
Grade G 070
Copper refinery slag
Coal furnace slag
Figure A.1 — Layout and sequence of the photographic examples
shown in the last photograph appended to this part of ISO 8501
18 © ISO and SIS 2007 – All rights reserved

Bibliography
[1] ISO 8501-2, 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
[2] ISO 8502 (all parts), Preparation of steel substrates before
application of paints and related products — Tests for the
assessment of surface cleanliness
[3] ISO 8503 (all parts), Preparation of steel substrates before
application of paints and related products — Surface roughness
characteristics of blast-cleaned steel substrates
[4] ISO 8504-2, Preparation of steel substrates before application of
paints and related products — Surface preparation methods —
Part 2: Abrasive blast-cleaning
[5] ISO 8504-3, Preparation of steel substrates before application of
paints and related products — Surface preparation methods —
Part 3: Hand- and power-tool cleaning
[6] ISO 11124-2, Preparation of steel substrates before application of
paints and related products — Specifications for metallic blast-
cleaning abrasives — Part 2: Chilled-iron grit
[7] ISO 11124-3, 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
[8] ISO 11125-3, Preparation of steel substrates before application of
paints and related products — Test methods for metallic blast-
cleaning abrasives — Part 3: Determination of hardness
© ISO and SIS 2007 – All rights reserved 19

[9] ISO 11126-3, Preparation of steel substrates before application of
paints and related products — Specifications for non-metallic blast-
cleaning abrasives — Part 3: Copper refinery slag
[10] ISO 11126-4, Preparation of steel substrates before application of
paints and related products — Specifications for non-metallic blast-
cleaning abrasives — Part 4: Coal furnace slag

20 © ISO and SIS 2007 – All rights reserved

Sommaire Page
Avant-propos .24
Introduction.26
1 Domaine d'application .29
2 Degrés de rouille.30
3 Degrés de préparation .31
4 Mode opératoire pour l'évaluation visuelle des subjectiles
d'acier .34
5 Photographies.35
Annexe A (informative) Photographies de référence du
changement d'aspect du subjectile après décapage
à l'aide de différents abrasifs.38
Bibliographie.42

© ISO et SIS 2007 – Tous droits réservés 23

Avant-propos
L'ISO (Organisation internationale de normalisation) est une fédération
mondiale d'organismes nationaux de normalisation (comités membres de
l'ISO). L'élaboration des Normes internationales est en général confiée aux
comités techniques de l'ISO. Chaque comité membre intéressé par une
étude a le droit de faire partie du comité technique créé à cet effet. Les
organisations internationales, gouvernementales et non gouvernementales,
en liaison avec l'ISO participent également aux travaux. L'ISO collabore
étroitement avec la Commission électrotechnique internationale (CEI) en
ce qui concerne la normalisation électrotechnique.
Les Normes internationales sont rédigées conformément aux règles
données dans les Directives ISO/CEI, Partie 2.
La tâche principale des comités techniques est d'élaborer les Normes
internationales. Les projets de Normes internationales adoptés par les
comités techniques sont soumis aux comités membres pour vote. Leur
publication comme Normes internationales requiert l'approbation de 75 %
au moins des comités membres votants.
L'attention est appelée sur le fait que certains des éléments du présent
document peuvent faire l'objet de droits de propriété intellectuelle ou de
droits analogues. L'ISO ne saurait être tenue pour responsable de ne pas
avoir identifié de tels droits de propriété et averti de leur existence.
L'ISO 8501-1 a été élaborée par le comité technique ISO/TC 35, Peintures
et vernis, sous-comité SC 12, Préparation de subjectiles d'acier avant
application de peintures et de produits assimilés.
Cette deuxième édition annule et remplace la première édition
(ISO 8501-1:1988). La modification principale concerne l'inclusion dans
l'Annexe A du Supplément informatif ISO 8501-1:1988/Suppl.1994.
24 © ISO et SIS 2007 – Tous droits réservés

L'ISO 8501 comprend les parties suivantes, présentées sous le titre
général Préparation de subjectiles d'acier avant application de peintures et
de produits assimilés — Évaluation visuelle de la propreté d'un subjectile:
⎯ Partie 1: Degrés de rouille et degrés de préparation des subjectiles
d'acier non recouverts et des subjectiles d'acier après décapage sur
toute la surface des revêtements précédents
⎯ Partie 2: Degrés de préparation des subjectiles d'acier précédemment
revêtus après décapage localisé des couches
⎯ Partie 3: Degrés de préparation des soudures, arêtes et autres zones
présentant des imperfections
⎯ Partie 4: États de surface initiaux, degrés de préparation et degrés de
fleurette de rouille après décapage à l'eau sous haute pression

© ISO et SIS 2007 – Tous droits réservés 25

Introduction
L'efficacité des revêtements de protection par peintures et produits
assimilés appliqués sur l'acier est nettement affectée par l'état du subjectile
immédiatement avant l'application de la peinture. Les principaux facteurs
dont l'influence est connue pour affecter cette efficacité sont
a) la présence de rouille et de calamine;
b) la présence d'agents de contamination de surface notamment les sels,
la poussière, les huiles et les graisses;
c) le profil de surface.
Les Normes internationales ISO 8501, ISO 8502 et ISO 8503 ont été
élaborées afin de fournir des méthodes d'évaluation de ces facteurs, alors
que l'ISO 8504 fournit des directives sur les méthodes de préparation
existantes pour le nettoyage des subjectiles d'acier, en indiquant pour
chacune la capacité d'atteindre des niveaux de propreté spécifiés.
Ces Normes internationales ne comportent aucune recommandation quant
aux systèmes de revêtement de protection à appliquer sur le subjectile
d'acier. Elles ne comportent pas non plus de recommandation quant aux
exigences de qualité du subjectile dans des cas particuliers, bien que ce
facteur puisse avoir une influence directe sur le choix du revêtement de
protection à appliquer et sur son efficacité. On trouvera de telles
recommandations dans d'autres documents tels que des Normes
nationales et des codes d'utilisation. Il est nécessaire que les utilisateurs de
ces Normes internationales s'assurent que les qualités spécifiées
⎯ sont compatibles et adaptées tant à l'environnement auquel l'acier
sera exposé qu'aux revêtements de protection à utiliser;
⎯ s'inscrivent dans les limites possibles du mode de nettoyage spécifié.
26 © ISO et SIS 2007 – Tous droits réservés

Les quatre Normes internationales auxquelles il est fait référence ci-dessus
traitent des aspects suivants de la préparation des subjectiles d'acier:
ISO 8501 — Évaluation visuelle de la propreté d'un subjectile;
ISO 8502 — Essais pour l'évaluation de la propreté d'un subjectile;
ISO 8503 — Caractéristiques de rugosité des subjectiles d'acier
décapés;
ISO 8504 — Méthodes de préparation des surfaces.
Chacune de ces Normes internationales est à son tour divisée en parties
séparées.
La présente partie de l'ISO 8501 identifie quatre niveaux (désignés par
«degrés de rouille») de calamine et de rouille couramment rencontrés sur
des surfaces d'acier non recouvert, monté ou en stock. Elle identifie
également certains degrés de propreté appréciée à l'œil nu (désignés par
«degrés de préparation») après préparation des subjectiles d'acier non
recouverts et des subjectiles d'acier après décapage général des
revêtements antérieurs. Ces degrés de propreté appréciés à l'œil nu sont
corrélés aux méthodes classiques de nettoyage de surface utilisées avant
mise en peinture.
La présente partie de l'ISO 8501 a pour but de fournir un outil d'évaluation
visuelle des degrés de rouille et des degrés de préparation. Elle comporte
28 photographies représentatives.
Quatorze de ces photographies montrent des subjectiles d'acier traités par
décapage à sec en utilisant du sable de quartz comme abrasif. L'usage
d'autres abrasifs peut affecter l'aspect du subjectile. Des modifications de
couleur causées par différents abrasifs sont illustrées dans l'Annexe A.
NOTE Vingt-quatre de ces photographies proviennent de la norme suédoise
SIS 05 59 00-1967, Degrés de rouille des surfaces d'acier et degrés de soins lors
du traitement préalable de ces surfaces pour la peinture anticorrosive. Les quatre
autres photographies proviennent de la norme allemande DIN 55 928, Partie 4,
Supplément 1 (août 1978), Protection des constructions d'acier contre la corrosion
par application de couches organiques et revêtements métalliques; préparation et
examen de surfaces; photographies de référence.
© ISO et SIS 2007 – Tous droits réservés 27

NORME INTERNATIONALE ISO 8501-1:2007(F)

Préparation des subjectiles d'acier avant
application de peintures et de produits
assimilés — Évaluation visuelle de la propreté
d'un subjectile —
Partie 1:
Degrés de rouille et degrés de préparation
des subjectiles d'acier non recouverts et
des subjectiles d'acier après décapage sur toute
la surface des revêtements précédents
1 Domaine d'application
La présente partie de l'ISO 8501 spécifie une série de degrés de rouille et
de degrés de préparation des subjectiles d'acier (voir Articles 2 et 3
respectivement). Les différents degrés font l'objet de descriptions écrites
accompagnées de clichés photographiques qui sont des exemples
représentatifs dans les limites de tolérance pour chacun des degrés décrits.
Elle est applicable aux subjectiles en acier laminé à chaud, préparés pour
être mis en peinture à l'aide de méthodes telles que décapage, nettoyage à
la main et à la machine, nettoyage à la flamme, bien que ces méthodes
donnent rarement des résultats comparables. Ces méthodes sont à la base
prévues pour l'acier laminé à chaud, mais les méthodes de décapage, en
particulier, peuvent également être utilisées sur l'acier laminé à froid
d'épaisseur suffisante pour supporter les déformations causées par l'impact
de l'abrasif ou les effets du nettoyage à la machine.
© ISO et SIS 2007 – Tous droits réservés 29

La présente partie de l'ISO 8501 est également applicable aux subjectiles
d'acier qui présentent des résidus bien adhérents de peinture et d'autres
particules étrangères (voir Note 2 en 3.1) en plus des résidus de calamine.
NOTE 1 Les degrés de préparation de subjectiles d'acier préalablement peints
[1]
après décapage local des couches de peinture font l'objet de l'ISO 8501-2 .
La présente partie de l'ISO 8501 établit un rapport entre la propreté du
subjectile et son aspect à l'œil nu. Cela est suffisant dans de nombreux cas
mais pour des revêtements susceptibles d'être exposés à des ambiances
rigoureuses, telles que l'immersion dans l'eau ou la condensation
permanente, il conviendra de faire des mesures sur les sels solubles et
autres agents de contamination invisibles sur une surface apparemment
propre à l'aide de méthodes physiques et chimiques qui font l'objet des
[2]
différentes parties de l'ISO 8502 . Les caractéristiques de rugosité du
subjectile devraient également être étudiées en référence aux différentes
[3]
parties de l'ISO 8503 .
NOTE 2 La présente partie de l'ISO 8501 contient le texte dans deux des trois
langues officielles de l'ISO, l'anglais et le français. Elle contient également le texte
en allemand, publié sous la responsabilité du DIN, et le texte en suédois, publié
sous la responsabilité du SIS.
2 Degrés de rouille
Quatre degrés de rouille sont spécifiés, désignés respectivement par A, B,
C et D. Ces degrés de rouille sont définis par des descriptions écrites.
A Subjectile d'acier largement recouvert de calamine adhérente mais
avec un peu ou pas du tout de rouille.
B Subjectile d'acier qui a commencé à rouiller et d'où la calamine a
commencé à s'écailler.
C Subjectile d'acier où la calamine a disparu sous l'action de la rouille ou
peut en être détachée par grattage mais qui présente quelques
chancres de rouille observables à l'œil nu.
D Subjectile d'acier où la calamine a
...