SIST EN ISO 16701:2025

SLOVENSKI STANDARD
01-oktober-2025
Korozija kovin in zlitin - Korozija v umetni atmosferi - Preskus pospešene korozije
z izpostavljanjem nadzorovanim pogojem izmeničnega vlaženja in vmesnim
pršenjem slanice (ISO 16701:2025)
Corrosion of metals and alloys - Corrosion in artificial atmosphere - Accelerated
corrosion test involving exposure under controlled conditions of humidity cycling and
intermittent spraying of a salt solution (ISO 16701:2025)
Korrosion von Metallen und Legierungen - Korrosion in künstlicher Atmosphäre -
Beschleunigte Korrosionsprüfungen unter zyklischer Einwirkung von Luftfeuchte und
intermittierendem Versprühen einer Salzlösung unter kontrollierten Bedingungen (ISO
16701:2025)
Corrosion des métaux et alliages - Corrosion en atmosphère artificielle - Essai de
corrosion accélérée comprenant des expositions sous conditions contrôlées à des cycles
d'humidité et à des vaporisations intermittentes de solution saline (ISO 16701:2025)
Ta slovenski standard je istoveten z: EN ISO 16701:2025
ICS:
77.060 Korozija kovin Corrosion of metals
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 16701
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2025
EUROPÄISCHE NORM
ICS 77.060 Supersedes EN ISO 16701:2015
English Version
Corrosion of metals and alloys - Corrosion in artificial
atmosphere - Accelerated corrosion test involving
exposure under controlled conditions of humidity cycling
and intermittent spraying of a salt solution (ISO
16701:2025)
Corrosion des métaux et alliages - Corrosion en Korrosion von Metallen und Legierungen - Korrosion
atmosphère artificielle - Essai de corrosion accélérée in künstlicher Atmosphäre - Beschleunigte
comprenant des expositions sous conditions contrôlées Korrosionsprüfungen unter zyklischer Einwirkung von
à des cycles d'humidité et à des vaporisations Luftfeuchte und intermittierendem Versprühen einer
intermittentes de solution saline (ISO 16701:2025) Salzlösung unter kontrollierten Bedingungen (ISO
16701:2025)
This European Standard was approved by CEN on 7 June 2025.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 16701:2025 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 16701:2025) has been prepared by Technical Committee ISO/TC 156
"Corrosion of metals and alloys" in collaboration with Technical Committee CEN/TC 262 “Metallic and
other inorganic coatings, including for corrosion protection and corrosion testing of metals and alloys”
the secretariat of which is held by BSI.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by December 2025, and conflicting national standards
shall be withdrawn at the latest by December 2025.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 16701:2015.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 16701:2025 has been approved by CEN as EN ISO 16701:2025 without any modification.

International
Standard
ISO 16701
Third edition
Corrosion of metals and alloys —
2025-06
Corrosion in artificial atmosphere
— Accelerated corrosion test
involving exposure under controlled
conditions of humidity cycling
and intermittent spraying of a salt
solution
Corrosion des métaux et alliages — Corrosion en atmosphère
artificielle — Essai de corrosion accélérée comprenant des
expositions sous conditions contrôlées à des cycles d'humidité et à
des vaporisations intermittentes de solution saline
Reference number
ISO 16701:2025(en) © ISO 2025
ISO 16701:2025(en)
© ISO 2025
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
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or ISO’s member body in the country of the requester.
ISO copyright office
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CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
ISO 16701:2025(en)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Apparatus . 2
4.1 General .2
4.2 Basic properties of the climate test chamber .3
4.3 Supporting requisites and accessories .3
5 Test method . 4
5.1 Test exposure conditions .4
5.2 Requirements on salt solution .10
5.3 Precipitation rate of salt solution .10
5.4 Start and end time of test .11
5.5 Duration of test .11
6 Test object conditions .11
6.1 Requirements on geometry and distribution .11
6.1.1 Test object orientation .11
6.1.2 Distribution of test objects . .11
6.1.3 Mass and total exposed surface of test objects .11
6.1.4 Test object support . 12
6.1.5 Test object exposure to salt spray . 12
6.2 Test object preparation . 13
6.2.1 Painted and scribed panels . 13
6.2.2 Other test object geometries . 13
6.2.3 Additional test conditions . 13
7 Requirements on quality control and calibration.13
7.1 Overview . 13
7.2 Climate control and calibration procedures .14
7.2.1 Definition of a climate deviation .14
7.2.2 Control procedure for basic compliance of test chamber . 15
7.3 Control of salt solution precipitation .16
7.3.1 General .16
7.3.2 Spray rack according to the example in Annex B .16
7.3.3 Other configurations for salt solution downfall .17
7.3.4 Visual control of spray patterns .17
7.4 Recommended schedule for quality control.18
7.4.1 Control before test start .18
7.4.2 Workday inspection . . .18
7.4.3 Weekly inspection .18
7.4.4 Six-month controls .18
7.4.5 Annual calibration and verification .18
7.5 Deviation handling .19
7.5.1 General .19
7.5.2 Test interruption .19
8 Evaluation of results . 19
9 Test report . 19
Annex A (normative) Requirements on test equipment .21
Annex B (informative) Example of a device for spraying a precipitation of salt solution .25

iii
ISO 16701:2025(en)
Annex C (informative) Guidelines on devices for independent, stand-alone temperature and
humidity monitoring .26
Annex D (normative) Temperature/humidity control procedures.27
Annex E (informative) Guiding information about the test method .30
Bibliography .38

iv
ISO 16701:2025(en)
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.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO’s adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 156, Corrosion of metals and alloys, in
collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 262,
Metallic and other inorganic coatings, including for corrosion protection and corrosion testing of metals and
alloys, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).
This third edition cancels and replaces the second edition (ISO 16701:2015), which has been technically
revised.
The main changes are as follows:
— The test cycle has been revised with the same intended acceptance criteria to improve field correlation
and reproducibility, when performed in various exposure chambers.
— An alternative cycle with alternating temperature in the climate cycling (constant dew point instead of
constant temperature) is introduced. It is a modification of the so called ACT1 (originally Volvo Standard
423-0014), however within the same scope and intended acceptance criteria.
— Extensive requirements and guidelines on quality assurance of test equipment and control procedures
have been incorporated, mainly as normative and informative annexes.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

v
ISO 16701:2025(en)
Introduction
Atmospheric corrosion of metallic materials, with or without corrosion protection, is influenced by many
environmental factors. Their corrosion impact varies with the type of exposed material system. It is
therefore not possible to design a laboratory corrosion test in such a way that the complexity and variations
of real, in-service conditions are fully represented. Acceleration (forced conditions) as such can also have a
negative impact on the correlation-to-field performance. Nevertheless, tests with humidity cycling and only
intermittent exposure to a salt solution provide a better correlation-to-field performance than tests using
continuous salt spray.
This document was developed in the automotive context, where the major contributor to corrosion is the
use of wintertime de-icing road salt in cool/cold temperate areas, most often as sodium chloride depositions
that act in cyclic humidity conditions. The test procedure is moderately forced by humidity and salt. It is
intended to be applicable for quality assurance of the metals and corrosion protections typically encountered
[1]-[4]
in motor vehicles. The method is also relevant in other areas of application, provided they have similar
[5][6]
climatic conditions with an influence of sodium chloride depositions.

vi
International Standard ISO 16701:2025(en)
Corrosion of metals and alloys — Corrosion in artificial
atmosphere — Accelerated corrosion test involving exposure
under controlled conditions of humidity cycling and
intermittent spraying of a salt solution
1 Scope
This document specifies an atmospheric accelerated test procedure in two closely related variants that
contain intermittent salt exposure combined with dynamic humidity patterns: variant A at constant dew
point and variant B at constant temperature. These variants are used in assessing the corrosion resistance
of metals in environments where there is a significant influence of chloride ions, mainly as sodium chloride
from, for example, winter road de-icing salt. The results obtained do not permit far-reaching conclusions on
the corrosion resistance of the tested metallic material under the whole range of environmental conditions
in which it can be used. Nevertheless, the method provides information on the relative corrosion resistance
of a material exposed to a salt-contaminated environment with varying humidity conditions.
The two accelerated laboratory corrosion test variants are applicable to:
— metals and their alloys (ferrous and non-ferrous);
— metallic coatings;
— chemical conversion coatings;
— organic coating on metals;
— a combination of materials and coatings that include galvanic interactions and/or crevice conditions.
NOTE 1 If testing low-alloy stainless steels according to this document, especially austenitic grades, there is a risk
of exaggerated pitting, which is not representative of most service environments.
NOTE 2 This document is not suitable for testing of wax and oil-based rust protection agents, due to the constantly
elevated temperature condition of the test.
This document also specifies requirements on the test equipment and contains detailed procedures for
quality control, including recommended instrumentation.
This document does not specify the dimensions of the tests specimens, the exposure period to be used for a
particular product, or the interpretation of the results. Such details are provided in the appropriate product
specifications.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp

ISO 16701:2025(en)
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
step
individual test climate operation, such as a linear climate ramp between two temperatures/humidities,
constant conditions during a defined time period or spraying with salt solution
3.2
sequence
series of steps (3.1)
Note 1 to entry: Sequences can be handled as subroutines when programming the test.
3.3
sub-cycle
sequence (3.2) when run in a repeated mode
3.4
test cycle
full weekly (168 h) series of different sub-cycles (3.3), to be repeated for a stipulated number of weeks
3.5
test area
area within a test chamber (usually horizontal and designed as a structure open to air circulation) onto
which test objects and their possible fixtures are supported
3.6
approved test area
part of the test area where the test conditions are fulfilled regarding climate and downfall of salt solution
3.7
test space
volume defined by the test area (3.5) times the permissible height to which the test object can extend without
compromising the stipulated uniformity of the test conditions
3.8
approved test space
approved test area (3.6) times the height where the test conditions are fulfilled regarding climate and
downfall of salt solution
3.9
tolerance span
permissible deviation ranges for the achieved momentaneous value of set temperature and relative humidity
relative to the programmed set value at any time increment
3.10
macro wetness
droplets or an aqueous film visible to the eye, e.g. from spray application or by dew formation
4 Apparatus
4.1 General
The climate test chamber shall offer a design so that the requirements on the test conditions in Clause 5
can be obtained and controlled within the permissible range according to the procedures in Clause 7. The
chamber test area and test space where these conditions are fulfilled are hence defined as the approved test
area and approved test space, respectively. The test chamber design, applicable for manufacturing and at
purchasing, shall be in accordance with Annex A.

ISO 16701:2025(en)
4.2 Basic properties of the climate test chamber
For a fully automated procedure, the chamber shall be equipped with a spray device capable of producing a
uniformly distributed spray of salt solution falling onto the test objects at a rate defined in 5.3. This can be
performed by installing a swaying rail or tube equipped with flat-spraying nozzles as depicted in Annex B.
Other technical solutions are permissible, provided they meet the downfall requirements.
4.3 Supporting requisites and accessories
The following requisites and accessories are necessary to perform the test method:
— Compressed, oil-free, clean air for humidification (if supplied by spray humidifiers), for cleaning salt
solution from spray nozzles and as a source for the renewal of chamber air. The supplier of the equipment
shall stipulate the specific requirements of the compressed air supply and may additionally include
special requirements, such as that it should meet ISO 8573-1, class 4 or better.
— A low-conductivity water supply for humidification or evaporative spray humidifiers and for the
preparation of salt solutions. The requirement on water quality for the equipment shall be set by the
supplier of the equipment. From corrosion testing standpoint, it is sufficient to be below 20 µS/cm. If the
humidification of the test chamber is supplied by high-pressure nozzle(s), the acceptable conductivity of
the water can be as low as 5 µS/cm to secure the long-term performance of nozzles and heaters.
— A tank for preparation and storage of salt solution or, alternatively, a system for direct in-line mixing
of water, saturated NaCl solution and, if applicable, diluted sulfuric acid to be contained within the
stipulated concentration and tolerances.
— A conductivity meter with built-in temperature compensation for preparation and control of the salt
solution.
— A standard pH-meter, with a glass-electrode for weak electrolytes, to be regularly calibrated at
pH = 7 and pH = 4.
— Sodium chloride of min 99,9 % purity without sodium iodide addition, either as a vacuum salt supplied
as grain salt or in accordance with the specification in ISO 9227.
— Sulfuric acid of reagent grade.
®1)
WARNING — Sulfuric acid (CAS Registry Number 7664-93-9) solution causes severe
skin burns and eye damage. Refer to safety data sheet for details. Handling of sulfuric acid
solution shall be restricted to skilled personnel or conducted under their control.
For accuracy, safety and convenience, it is recommended to use commercially available ampoules of
diluted sulfuric acid (titration reagent) as a source for the preparation of the solution. One litre of a 0,5 M
sulfuric acid solution prepared this way is sufficient for the acidification of 10 m of ready salt solution. In
the unlikely need to adjust up the pH of the ready salt solution, use diluted sodium hydroxide. For safety
reasons, it is recommended to prepare the solution from commercially available titration ampoules. A
0,01 M solution is convenient.
— A device for independent monitoring of temperature and relative humidity (RH) shall be accessible.
Annex C provides information on suitable devices. This instrument shall on stipulated intervals be used
for independent monitoring and calibration of the climate in the test space of the exposure chamber in
accordance with Annex D.
— Racks of inert material for support and aligned fixation of test object, which shall not hamper a free
airflow around the test objects, nor collect standing wetness. Further requirements are found in Clause 6.
— Funnels, beakers/measuring glasses and a balance with at least 0,1 g accuracy for monitoring and
calibration of salt solution downfall throughout the test plane of the exposure chamber. ®
1) Chemical Abstracts Service (CAS) Registry Number is a trademark of the American Chemical Society (ACS). This
information is given for the convenience of users of this document and does not constitute an endorsement by ISO of the
product named. Equivalent products may be used if they can be shown to lead to the same results.

ISO 16701:2025(en)
5 Test method
5.1 Test exposure conditions
There are two variants of the test procedure: variant A and variant B. Figure 1 gives an overview of the
weekly patterns of temperature and RH for the variants.
In variant A, the humidity cycling is run with a counter temperature cycling to receive approximately
constant absolute humidity/dew point. This is in line with outdoor day and night conditions. Variant B runs
with constant temperature during the humidity cycling and is recommended when heavy test objects are
exposed.
Biweekly in both test variants, a 3-h wet period of intermittent spray with salt solution is followed by a
controlled gradual drying-up for several hours (see Figure 2). This 24-h sequence is identical for variant
A and B, and is followed by a series of repeated 12-h climate cycles, which are different for variants A and
B (see Figure 3). The sequence of spraying followed by climate cycling is repeated once to reach a one-
week test cycle. This cycle is then repeated for a stipulated number of weeks (typically six weeks) to form
a complete atmospheric corrosion test. The background and rationales behind the two test variants and
guidelines when to use which are found in Annex E. Table 1 and Table 2 list the detailed exposure conditions
step by step for each test variant independently.

ISO 16701:2025(en)
a) Weekly overview of test variant A
b) Weekly overview of test variant B
Key
a
X elapsed time (h) Temperature, expressed in solid line.
b
Y1 temperature (°C) Relative humidity, expressed in dotted line.
Y2 relative humidity
Figure 1 — Complete one-week cycles of the test variants A and B

ISO 16701:2025(en)
a) Test variant A
b) Test variant B
Key
a
X elapsed time (h) Relative humidity, expressed in dotted line.
b
Y1 exposure temperature (°C) Temperature, expressed in solid line.
c
Y2 exposure relative humidity (% RH) Allowed tolerance span in temperature and relative
humidity, expressed in rasterized areas.
1 intermittent salt spray exposure
2 drying of corroded areas to 85 % RH
3 extended period of moderate drying
4 connection ramp to subsequent humidity cycling
Figure 2 — 24-h precipitation and drying sequence for test variants A and B

ISO 16701:2025(en)
a) Test variant A (constant dew point)
b) Test variant B (constant temperature)
Key
a
X elapsed time (h) Relative humidity, expressed in dotted line.
b
Y1 exposure temperature (°C) Temperature, expressed in solid line.
c
Y2 relative humidity (% RH) Allowed tolerance span in temperature and relative
humidity, expressed in rasterized areas.
Figure 3 — 12-h sequences with controlled temperature and humidity variation, used repeatedly
after 24-h sequence with precipitation

ISO 16701:2025(en)
The achieved values in temperature and RH shall be within the rasterized areas in Figures 2 and 3, depicting
the tolerance span from set values (see also 7.2.1). Numbers for the tolerance span are found in Table 1 and
Table 2. No rasterization means no requirements. The 3-h sequence of intermittent salt spray exposure
consists of six 5-min periods with spray and with a high humidity (95 % RH) set between the spray events
to maintain a consistent wet surface. It is permissible that the temperature drops up to 5 °C temporarily
during the spray events.
NOTE 1 The 3-h period at 85 % RH is designed to make evaporating macro wetness from areas of active corrosion
to terminate at a controlled humidity level, where corrosion is still active. This minimizes the variation in corrosion
due to differences in convective drying in different types of test chambers.
NOTE 2 The subsequent ramp and constant period at 70 % RH, 40 °C is designed to initiate pitting corrosion on
susceptible materials and to promote high activity in crevices during slow drying, but also to dry out the complete
chamber from macro wetness.
Table 1 — Test program for variant A, step by step, including requirements on climate control
Settings at start of step
Time Duration of
Step with tolerance span
elapsed step(s)
Comments
during step
no. h:m h:m T (°C) % RH
24-h sequence with precipitation, variant A
A:1 00:00 00:05 35 −5 wet Spray with 1,0 % NaCl solution pH = 4,1
Temperature or climate control, retained
A:2 00:05 00:25 35 ± 1 95 −
wetness
Repeat steps A:1 + A:2 five times, i.e. six spray
+ 5 × (A:1+A:2) 00:30 − 35 wet
periods in total
95 % RH nominal at start of drying
A:3 03:00 02:00 35 − 95 −
Ramping up temperature/down% RH
Drying of macro-wetness in corrosion nests
a a
A:4 05:00 03:00 37 ± 0,8 85 ± 4
at constant 85 % RH
A:5 08:00 04:00 37 ± 1 85 ± 5 Ramping up temperature/down % RH
A:6 12:00 10:00 40 ± 0,8 70 ± 4 Constant humidity at 70 % RH
Ramping down temperature/up% RH Trans-
A:7 22:00 02:00 40 ± 1 70 ± 5
fer to climate cycle A:8-A:11
24:00 − 35 95 Ending 24-h precipitation day
12 h climate cycle, variant A
A:8 24:00 03:00 35 ± 0,8 95 ± 4 Constant humidity at 95 % RH
A:9 27:00 03:00 35 ± 1 95 ± 5 Ramping up temperature/down% RH
A:10 30:00 03:00 45 ± 0,8 55 ± 4 Constant humidity at 55 % RH
A:11 33:00 03:00 45 ± 1 55 ± 5 Ramping down temperature/up% RH
36:00 - 35 95 Closing 12-h cycle
Test compilation, variant A:
1 ×
00:00 24:00 − − Run 24-h sequence with precipitation once
(A:1-A7)
+ 5 ×
24:00 60:00 − − Run 12-h climate cycle five times
(A8-A11)
1 ×
84:00 24:00 − − Run 24-h sequence with precipitation once
(A:1-A7)
+ 5 ×
108:00 60:00 − − Run 12-h climate cycle five times
(A8-A11)
Complete week Repeat complete week cycle for stipulated
168:00 − − −
cycle number of weeks
a
Tolerance span is introduced after 1 h.

ISO 16701:2025(en)
NOTE 3 The tolerance span for temperature and RH does not contain the errors associated with the independent
measuring device, which is chosen according to Annex C and calibrated to best standards.
Table 2 — Test program for variant B, step by step, including requirements on climate control
Settings at start of step
Time Duration of
Step with tolerance span
elapsed step(s)
Comments
during step
no. h:m h:m T (°C) % RH
24-h sequence with precipitation, variant B
B:1 00:00 00:05 35 −5 wet Spray with 1,0 % NaCl solution pH = 4,1
Temperature or climate control, retained
B:2 00:05 00:25 35 ± 1 95 −
wetness
Repeat steps B:1 + B:2 five times, i.e. six spray
+ 5 × (B:1+B:2) 00:30 − 35 wet
periods in total
95 % RH nominal at start of drying Ramping
B:3 03:00 02:00 35 − 95 −
up temp. and down% RH
Drying of macro-wetness in corrosion nests
a a
B:4 05:00 03:00 37 ± 0,8 85 ± 4
at constant 85 % RH
B:5 08:00 04:00 37 ± 1 85 ± 5 Ramping up temperature/down % RH
B:6 12:00 10:00 40 ± 0,8 70 ± 4 Constant humidity at 70 % RH
Ramping down temperature/up% RH Trans-
B:7 22:00 02:00 40 ± 1 70 ± 5
fer to climate cycle B:8-B11
24:00 − 40 95 Ending 24-h precipitation day
12-h climate cycle, variant B
B:8 24:00 02:30 40 ± 0,8 95 ± 4 Constant humidity at 95 % RH
B:9 26:30 03:00 40 ± 0,8 95 ± 4 Ramping up temperature/down% RH
B:10 29:30 03:30 40 ± 0,8 55 ± 4 Constant humidity at 55 % RH
B:11 33:00 03:00 40 ± 0,8 55 ± 4 Ramping down temperature/up% RH
36:00 − 40 95 Closing 12-h cycle
Test compilation, variant B:
1 ×
00:00 24:00 − − Run 24-h sequence with precipitation once
(B:1-B:7)
+ 5 ×
24:00 60:00 − − Run 12-h climate cycle five times
(B:8-B:11)
1 ×
84:00 24:00 − − Run 24-h sequence with precipitation once
(B:1-B:7)
+ 5 ×
108:00 60:00 − − Run 12-h climate cycle five times
(B:8-B:11)
Complete week Repeat complete week cycle for stipulated
168:00 − − −
cycle number of weeks
a
Tolerance span is introduced after 1 h.
NOTE 4 The tolerance span for temperature and RH does not contain the errors associated with the independent
measuring device, which is chosen according to Annex C and calibrated to best standards.
All utilized chamber test area shall meet the requirements in Table 1 or Table 2 (= approved test area), i.e. it
is not sufficient to rely on a single position measurement only, using an independent monitoring device or the
values given by the chamber control sensors. A basic uniformity control shall be performed in accordance
with 7.2 and Annex D for monitoring procedure.
It is permissible to deviate from the tolerance spans in Table 1 and Table 2 temporarily in association with
test object handling. This shall be restricted to Step 10 or 11 in the last climate cycle before precipitation.

ISO 16701:2025(en)
For both test variants A and B, it is permissible to move the second 24-h salt spray sequence in Figure 3 either
12 h forward or 12 h backwards in the mixed weekly succession, by moving a 12-h sequences according to
Figure 2 to the opposite side of the 24-h salt spray sequence. In this way, the start of both 24-h salt spray/
drying sequences can be synchronized into normal work hours (see Table 3). This measure has no significant
impact on the test results.
Table 3 — Permissible weekly succession of number of sequences for a full 168-h cycle
24-h precipita- 12-h 24-h precipita- 12-h
tion and drying controlled climate tion and drying controlled climate
Designation sequence 1 sequence sequence 2 sequence
(see Figure 1) (see Figure 2) (see Figure 1) (see Figure 2)
no. no. no no.
Symmetric (see Figure 3)
1 5 1 5
(shortest program)
Workhour synchronized precip-
1 4 1 6
itation, variant 1
Workhour synchronized precip-
1 6 1 4
itation, variant 2
NOTE 5 The non-symmetric variants 1 and 2 means that test starts are allowed twice weekly under a work hour
synchronized precipitation regime.
5.2 Requirements on salt solution
The test solution shall have a targeted concentration of 1,0 % (percent by mass) but may vary up to ±0,1 %,
to allow mixing in-line from concentrated solution by controlled dilution. The stipulated concentration
corresponds to a solution conductivity of 16,5 mS/cm ± 0,16 mS/cm (25 °C). If systematic offsets in concentration
are found over time, even if within the stipulated range, it is recommended to adjust for this to improve the
reproducibility of the test. The salt and deionized water shall at least be of the quality required in 4.2.
The 1 % NaCl solution shall be acidified to a pH value of 4,13 ± 0,1 through the addition of sulfuric acid to
-5
a concentration of 5 × 10 M, for example by adding 1,0 ml of 0,5 M H SO to 10 l of saline solution. (The
2 4
contribution from the acid to the conductivity is insignificant – 0,1 mS/cm). If, for any reason, pH becomes
too low, this may be compensated by adding minute amounts of sodium hydroxide solution. A 0,01 M solution
is usually suitable.
It is recommended to carefully prepare and store a standard reference solution of the composition given
-5
above. i.e. to prepare a 1,00 % NaCl solution, which also can contain 5,0 × 10 M sulfuric acid, diluted from a
well determined source.
Sprayed salt solution shall not be reused.
5.3 Precipitation rate of salt solution
The targeted precipitation rate of the salt solution is presented in Table 4 with permissible minimum and
maximum downfall rates as monitored by the procedure described in 7.3.1 and Figure 6.
Table 4 — Permissible ranges of downfall rate of sprayed solution onto horizontal test area
As downfall per 3-h precipitation se-
As continuous downfall quence (30 min in total)
mm/h ml/cm
Targeted average precipitation 15 0,75
Permissible minimum 10 0,5
Permissible maximum 30 1,5
ISO 16701:2025(en)
NOTE Regardless of application technique, it is usually difficult to avoid excess downfall in local chamber
positions when meeting the permissible local minimum downfall over the test area. Moderate excess downfall has no
significant impact on the test results and is reflected by the permissible maximum downfall value. Applying a volume
flow that corresponds to an average downfall of 15 mm/h is usually compatible with the local permissible minimum
and maximum downfalls.
5.4 Start and end time of test
For a continuously running chamber, the regular sta
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