IEC 60695-5-1:2021

IEC 60695-5-1 ®
Edition 3.0 2021-10
REDLINE VERSION
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STANDARD
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Fire hazard testing –
Part 5-1: Corrosion damage effects of fire effluent – General guidance

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IEC 60695-5-1 ®
Edition 3.0 2021-10
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
HORIZONTAL PUBLICATION
Fire hazard testing –
Part 5-1: Corrosion damage effects of fire effluent – General guidance
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.020 ISBN 978-2-8322-4440-1

– 2 – IEC 60695-5-1:2021 RLV © IEC 2021
CONTENTS
FOREWORD . 3
INTRODUCTION . 2
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 Fire scenarios and physical fire models . 9
5 General aspects of the corrosivity of fire effluent . 13
5.1 Corrosion damage scenarios . 13
5.2 Types of corrosion damage effects . 15
5.2.1 Introduction . 15
5.2.2 Metal loss . 15
5.2.3 Moving parts becoming immobile . 15
5.2.4 Bridging of conductor circuits . 15
5.2.5 Formation of a non-conducting layer on contact surfaces. 15
5.3 Factors affecting corrosivity . 16
5.3.1 Introduction . 16
5.3.2 The nature of fire effluent . 16
5.3.3 The corrosion environment . 17
6 Principles of corrosion damage measurement . 17
6.1 Introduction . 17
6.2 Generation of the fire effluent . 17
6.2.1 General . 17
6.2.2 Selection of the test specimen to be burned . 18
6.2.3 Selection of the physical fire model . 18
6.3 Assessment of corrosive potential . 18
6.3.1 General . 18
6.3.2 Indirect assessment . 18
6.3.3 Simulated product testing . 19
6.3.4 Product testing . 19
6.4 Consideration of corrosivity test methods . 20
7 Relevance of data to hazard assessment . 21
Bibliography . 23

Figure 1 – Different stages in the development of a fire within a compartment . 13
Figure 2 – Evaluation and consideration of corrosion damage test methods . 21

Table 1 – General classification of fires (ISO/TR 9122-1) .
Table 1 – Characteristics of fire stages (from Table 1 of ISO 19706:2011) . 14
Table 2 – Summary of corrosivity test methods . 19

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FIRE HAZARD TESTING –
Part 5-1: Corrosion damage effects of fire effluent –
General guidance
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This redline version of the official IEC Standard allows the user to identify the changes made to
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change has been made. Additions are in green text, deletions are in strikethrough red text.

– 4 – IEC 60695-5-1:2021 RLV © IEC 2021
International Standard IEC 60695-5-1 has been prepared by IEC technical committee 89: Fire
hazard testing.
This third edition cancels and replaces the second edition, published in 2002, and constitutes
a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) References to IEC TS 60695-5-3 (withdrawn in 2014) have been removed.
b) References to IEC 60695-1-1 are now to its replacements: IEC 60695-1-10 and
IEC 60695-1-11.
c) ISO/TR 9122-1 has been revised by ISO 19706.
d) Table 1 has been updated.
e) References to ISO 11907-2 and ISO 11907-3 have been removed.
f) Terms and definitions have been updated.
g) Text in 6.4 has been updated.
h) Bibliographic references have been updated.
The text of this International Standard is based on the following documents:
FDIS Report on voting
89/1539/FDIS 89/1543/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement,
available at www.iec.ch/members_experts/refdocs. The main document types developed by
IEC are described in greater detail at www.iec.ch/standardsdev/publications.
It has the status of a basic safety publication in accordance with IEC Guide 104 and
ISO/IEC Guide 51.
In this standard, the following print types are used:
Arial bold: terms referred to in Clause 2
This standard is to be read in conjunction with IEC TS 60695-5-2.
A list of all parts in the IEC 60695 series, published under the general title Fire hazard testing,
can be found on the IEC website.

The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates that it
contains colours which are considered to be useful for the correct understanding of its
contents. Users should therefore print this document using a colour printer.

– 6 – IEC 60695-5-1:2021 RLV © IEC 2021
INTRODUCTION
The risk of fire should be considered in any electrical circuit. With regard to this risk, the
circuit and equipment design, the selection of components and the choice of materials should
contribute towards reducing the likelihood of fire even in the event of foreseeable abnormal
use, malfunction or failure. The practical aim should be to prevent ignition caused by electrical
malfunction but, if ignition and fire occur, to control the fire preferably within the bounds of the
enclosure of the electrotechnical product.
In the design of an electrotechnical product the risk of fire and the potential hazards
associated with fire need to be considered. In this respect the objective of component, circuit
and equipment design, as well as the choice of materials, is to reduce the risk of fire to a
tolerable level even in the event of reasonably foreseeable (mis)use, malfunction or failure.
IEC 60695-1-10, IEC 60695-1-11, and IEC 60695-1-12 [1] provide guidance on how this is to
be accomplished.
Fires involving electrotechnical products can also be initiated from external non-electrical
sources. Considerations of this nature are dealt with in an overall fire hazard assessment.
The aim of the IEC 60695 series is to save lives and property by reducing the number of fires
or reducing the consequences of the fire. This can be accomplished by:
• trying to prevent ignition caused by an electrically energised component part and, in the
event of ignition, to confine any resulting fire within the bounds of the enclosure of the
electrotechnical product.
• trying to minimise flame spread beyond the product’s enclosure and to minimise the
harmful effects of fire effluents including heat, smoke, and toxic or corrosive combustion
products.
All fire effluent is corrosive to some degree and the level of potential to corrode depends on
the nature of the fire, the combination of combustible materials involved in the fire, the nature
of the substrate under attack, and the temperature and relative humidity of the environment in
which the corrosion damage is taking place. There is no evidence that fire effluent from
electrotechnical products offers greater risk of corrosion damage than the fire effluent from
other products such as furnishings, or building materials, etc.
The performance of electrical and electronic components can be adversely affected by
corrosion damage when subjected to fire effluent. A wide variety of combinations of small
quantities of effluent gases, smoke particles, moisture and temperature may provide
conditions for electrical component or system failures from breakage, overheating or shorting.
Evaluation of potential corrosion damage is particularly important for high value and safety-
related electrotechnical products and installations.
Technical committees responsible for products will choose the test(s) and specify the level of
severity.
The study of corrosion damage requires an interdisciplinary approach involving chemistry,
electricity, physics, mechanical engineering, metallurgy and electrochemistry. In the
preparation of this part of IEC 60695-5, all of the above have been considered.
IEC 60695-5-1 defines the scope of the guidance and indicates the field of application.
IEC TS 60695-5-2 provides a summary of test methods including relevance and usefulness.
___________
Numbers in square brackets refer to the bibliography.

IEC 60695-5-3 provides details of a small-scale test method for the measurement of leakage
current and metal loss caused by fire effluent.

– 8 – IEC 60695-5-1:2021 RLV © IEC 2021
FIRE HAZARD TESTING –
Part 5-1: Corrosion damage effects of fire effluent –
General guidance
1 Scope
This part of IEC 60695 provides guidance on the following:
a) general aspects of corrosion damage test methods;
b) methods of measurement of corrosion damage;
c) consideration of test methods;
d) relevance of corrosion damage data to hazard assessment.
This basic safety publication is primarily intended for use by technical committees in the
preparation of standards in accordance with the principles laid down in IEC Guide 104 and
ISO/IEC Guide 51. It is not intended for use by manufacturers or certification bodies.
One of the responsibilities of a technical committee is, wherever applicable, to make use of
basic safety publications in the preparation of its publications. The requirements, test
methods or test conditions of this basic safety publication will not apply unless specifically
referred to or included in the relevant publications.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60695-1-1:1999, Fire hazard testing – Part 1-1: Guidance for assessing the fire hazard
of electrotechnical products – General guidelines
IEC/TS 60695-5-2:2002, Fire hazard testing – Part 5-2: Corrosion damage effects of fire
effluent – Summary and relevance of test methods
IEC/TS 60695-5-3, Fire hazard testing – Part 5-3: Corrosion damage effects of fire effluent –
Leakage current and metal loss test method
IEC 60754-1:1994, Test on gases evolved during combustion of materials from cables –
Part 1: Determination of the amount of halogen acid gas
IEC 60754-2:1991, Test on gases evolved during combustion of electric cables – Part 2:
Determination of degree of acidity of gases evolved during the combustion of materials taken
from electric cables by measuring pH and conductivity
IEC 60754-2, Amendment 1 (1997)
ISO/TR 9122-1:1989, Toxicity testing of fire effluents – Part 1: General
___________
To be published.
ISO 11907-2:1995, Plastics – Smoke generation – Determination of the corrosivity of fire
effluents – Part 2: Static method
ISO 11907-3:1998, Plastics – Smoke generation – Determination of the corrosivity of fire
effluents – Part 3: Dynamic decomposition method using a travelling furnace
ISO 11907-4:1998, Plastics – Smoke generation – Determination of the corrosivity of fire
effluents – Part 4: Dynamic decomposition method using a conical radiant heater
ISO/IEC 13943:2000, Fire safety – Vocabulary
ASTM D 2671 – 00, Standard Test Methods for Heat-Shrinkable Tubing for Electrical Use
IEC 60695-1-10, Fire hazard testing – Part 1-10: Guidance for assessing the fire hazard of
electrotechnical products – General guidelines
IEC 60695-1-11, Fire hazard testing – Part 1-11: Guidance for assessing the fire hazard of
electrotechnical products – Fire hazard assessment
IEC TS 60695-5-2, Fire hazard testing – Part 5-2: Corrosion damage effects of fire effluent –
Summary and relevance of test methods
IEC GUIDE 104, The preparation of safety publications and the use of basic safety
publications and group safety publications
ISO/IEC Guide 51, Safety aspects – Guidelines for their inclusion in standards
ISO 11907-1:2019, Plastics – Smoke generation – Determination of the corrosivity of fire
effluents – Part 1: General concepts and applicability
ISO 13943:2017, Fire safety – Vocabulary
ISO 19706:2011, Guidelines for assessing the fire threat to people
3 Terms and definitions
For the purposes of this document, the following terms and definitions, some of which have
been taken from ISO/IEC 13943, apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
corrosion damage
physical and/or chemical damage or impaired function caused by chemical action
[SOURCE: ISO/IEC 13943, definition 25 ISO 13943:2017, 3.69]
3.2
corrosion target
sensor used to determine the degree of corrosion damage (3.1), under specified conditions

– 10 – IEC 60695-5-1:2021 RLV © IEC 2021
Note 1 to entry: This sensor may be a product, a component, or a reference material used to simulate them. It
may also be a reference material or object used to simulate the behaviour of a product or a component.
[SOURCE: ISO/IEC 13943, definition 26 ISO 13943:2017, 3.70]
3.3
critical relative humidity
level of relative humidity that causes leakage current to exceed a value defined in the product
specification
3.3
fire decay
stage of fire development after a fire has reached its maximum intensity and during which the
heat release rate and the temperature of the fire are decreasing
[SOURCE: ISO 13943:2017, 3.122]
3.4
fire effluent
totality of all gases and/or aerosols, (including suspended particles), created by combustion
or pyrolysis (3.9) and emitted to the environment
[SOURCE: ISO/IEC 13943, definition 45 ISO 13943:2017, 3.123]
3.5
fire effluent decay characteristics
physical and/or chemical changes in fire effluent due to time and transport
3.6
fire effluent transport
movement of fire effluent away from the location of the fire
3.5
fire scenario
detailed description of conditions, including environmental, of one or more stages from before
ignition to after completion of combustion in an actual fire at a specific location or in a real-
scale simulation
[ISO/IEC 13943, definition 58]
qualitative description of the course of a fire with respect to time, identifying key events that
characterize the studied fire and differentiate it from other possible fires
Note 1 to entry: See fire scenario cluster (ISO 13943:2017, 3.154) and representative fire scenario
(ISO 13943:2017, 3.153).
Note 2 to entry: It typically defines the ignition and fire growth processes, the fully developed fire stage, the fire
decay (3.3) stage, and the environment and systems that will impact on the course of the fire.
Note 3 to entry: Unlike deterministic fire analysis, where fire scenarios are individually selected and used as
design fire scenarios, in fire risk assessment, fire scenarios are used as representative fire scenarios within fire
scenario clusters.
[SOURCE: ISO 13943:2017, 3.152]
3.8
ignition source
source of energy that initiates combustion
([SO/IEC 13943, definition 97]

3.6
flashover
transition to a state of total surface involvement in a fire of combustible
materials within an enclosure
[SOURCE: ISO 13943:2017, 3.184]
3.7
full developed fire
state of total involvement of combustible materials in a fire
[SOURCE: ISO 13943:2017, 3.192]
3.8
leakage current
electrical current flowing in an undesired circuit
3.9
physical fire model
laboratory process, including the apparatus, the environment and the fire test procedure
intended to represent a certain phase of a fire
[SOURCE: ISO 13943:2017, 3.298]
3.10
pyrolysis
chemical decomposition of a substance by the action of heat
Note 1 to entry: Pyrolysis is often used to refer to a stage of fire before flaming combustion has begun.
Note 2 to entry: In fire science, no assumption is made about the presence or absence of oxygen.
[SOURCE: ISO 13943:2017, 3.316]
3.11
small-scale fire test
fire test performed on a test specimen of small dimensions
Note 1 to entry: There is no clear upper limit for the dimensions of the test specimen in a small-scale fire test. In
some instances, a fire test performed on a test specimen with a maximum dimension of less than 1 m is called a
small-scale fire test. However, a fire test performed on a test specimen of which the maximum dimension is
between 0,5 m and 1,0 m is often called a medium-scale fire test.
[SOURCE: ISO 13943:2017, 3.346]
3.12
smoke
visible part of a fire effluent
[SOURCE: ISO/IEC 13943, definition 150 ISO 13943:2017, 3.347]

– 12 – IEC 60695-5-1:2021 RLV © IEC 2021
4 Fire scenarios and physical fire models
During recent years, major advances have been made in the analysis of fire effluents. It is
recognized that the composition of the mixture of combustion products is particularly
dependent upon the nature of the combusting materials, the prevailing temperatures and the
ventilation conditions, especially access of oxygen to the seat of the fire. Table 1 shows how
the different stages of a fire relate to the changing atmosphere. Conditions for use in
laboratory scale tests can be derived from the table in order to correspond, as far as possible,
to full-scale fires.
Fire involves a complex and interrelated array of physical and chemical phenomena. As a
result, it is difficult to simulate all aspects of a real fire in laboratory scale apparatus. This
problem of fire model validity is perhaps the single most perplexing technical problem
associated with all fire testing.
General guidance for assessing the fire hazard of electrotechnical products is given in
IEC 60695-1-10. Guidance concerning fire hazard assessment is given in IEC 60695-1-11.
ISO 11907-1 defines terms related to smoke corrosivity as well as smoke acidity and smoke
toxicity. It presents the scenario-based approach that controls smoke corrosivity. It describes
the test methods to assess smoke corrosivity at laboratory scale and deals with test
applicability and post-exposure conditions.
After ignition, fire development may occur in different ways depending on the environmental
conditions, as well as on the physical arrangement of the combustible materials. However, a
general pattern can be established for fire development within a compartment, where the
general temperature-time curve shows three stages, plus a fire decay stage (see Figure 1).
Stage 1 (non-flaming decomposition) is the incipient stage of the fire prior to sustained
flaming, with little rise in the fire room temperature. Ignition and smoke generation are the
main hazards during this stage.
Stage 2 (developing fire) starts with ignition and ends with a rapid rise in fire room
temperature. Spread of flame and heat release are the main hazards in addition to smoke
during this stage.
Stage 3 (fully developed fire) starts when the surface of all of the combustible contents of the
room has decomposed to such an extent that sudden ignition occurs all over the room, with a
rapid and large increase in temperature (flashover).
At the end of Stage 3, the combustibles and/or oxygen have been largely consumed and
hence the temperature decreases at a rate which depends on the ventilation and the heat and
mass transfer characteristics of the system. This is known as the fire decay stage.
In each of these stages, a different mixture of decomposition products may be formed and
this, in turn, influences the corrosive potential of the fire effluent produced during that stage.
Characteristics of these fire stages are given in Table 1.

Figure 1 – Different stages in the development of a fire within a compartment
Table 1 – General classification of fires (ISO/TR 9122-1)
Oxygen * CO2/CO Temperature * Irradiance ***
Stages of fire
ratio **
°
−2
% C kW⋅m
Stage 1 Non-flaming decomposition
a) Smouldering (self-sustaining) 21 Not applicable <100 Not applicable
b) Non-flaming (oxidative) 5 to 21 Not applicable <500 <25
c) Non-flaming (pyrolytic) <5 Not applicable <1 000 Not applicable
Stage 2 Developing fire (flaming) 10 to 15 100 to 200 400 to 600 20 to 40
Stage 3 Fully developed fire (flaming)
a) Relatively low ventilation 1 to 5 <10 600 to 900 40 to 70
b) Relatively high ventilation 5 to 10 <100 600 to 1 200 50 to 150
* General environmental condition (average) within compartment.
** Mean value in fire plume near to fire.
*** Incident irradiance onto test specimen (average).

5 General aspects of the corrosivity of fire effluent
5.1 Corrosion damage scenarios
With respect to electrotechnical equipment and systems, there are three corrosion damage
scenarios which are of concern. These are where corrosion damage is caused by fire effluent
in the following situations:
a) within electrotechnical equipment and systems when exposed to fire effluent caused by
unusual, localized, internal sources of excessive heat and ignition;
b) within electrotechnical equipment and systems when exposed to fire effluent caused by
external sources of flame or excessive heat;
c) within building structures when exposed to fire effluent emitted from electrotechnical
equipment and systems.
– 14 – IEC 60695-5-1:2021 RLV © IEC 2021

Table 1 – Characteristics of fire stages (from Table 1 of ISO 19706:2011)
Max. temperature Oxygen volume
[CO]
Heat flux to
100×[CO2]
Fuel/air %
fuel surface
[CO2]
Fire stage °C % equivalence
([CO2]+[CO])
ratio (plume)
2 efficiency
kW/m Fuel surface Upper layer Entrained Exhausted v/v
1. Non-flaming
a. self-sustaining not
d
450 to 800 25 to 85 20 20 – 0,1 to 1 50 to 90
(smouldering) applicable
b. oxidative pyrolysis from
b c c
externally applied – 300 to 600 a 20 20 < 1
radiation
c. anaerobic pyrolysis from
b c c
externally applied – 100 to 500 0 0 >> 1
radiation
d e
2. Well-ventilated flaming 0 to 60 350 to 650 50 to 500 ≈ 20 ≈ 20 < 1 < 0,05 > 95
f
3. Underventilated flaming
a. small, localized fire,
a
generally in a poorly
0 to 30 300 to 600 50 to 500 15 to 20 5 to 10 > 1 0,2 to 0,4 70 to 80
ventilated compartment
g h i
b. post-flashover fire 50 to 150 350 to 650 > 600 < 15 < 5 > 1 0,1 to 0,4 70 to 90
a
The upper limit is lower than for well-ventilated flaming combustion of a given combustible.
b
The temperature in the upper layer of the fire room is most likely determined by the source of the externally applied radiation and room geometry.
c
There are few data, but for pyrolysis this ratio is expected to vary widely depending on the material chemistry and the local ventilation and thermal conditions.
d
The fire’s oxygen consumption is small compared to that in the room or the inflow, the flame tip is below the hot gas upper layer or the upper layer is not yet significantly
vitiated to increase the CO yield significantly, the flames are not truncated by contact with another object, and the burning rate is controlled by the availability of fuel.
e
The ratio can be up to an order of magnitude higher for materials that are fire-resistant. There is no significant increase in this ratio for equivalence ratios up to ≈ 0,75.
Between ≈ 0,75 and 1, some increase in this ratio may occur.
f
The fire’s oxygen demand is limited by the ventilation opening(s); the flames extend into the upper layer.
g
Assumed to be similar to well-ventilated flaming.
h
The plume equivalence ratio has not been measured; the use of a global equivalence ratio is inappropriate.
i
Instances of lower ratios have been measured. Generally, these result from secondary combustion outside the room vent.

5.2 Types of corrosion damage effects
5.2.1 Introduction
Four types of corrosion damage effect are recognized. These are
a) metal loss,
b) moving parts becoming immobile,
c) bridging of conductor circuits,
d) formation of a non-conducting layer on contact surfaces.
5.2.2 Metal loss
Metal loss is caused by oxidation of elemental metal to a positive oxidation state. One of the
simplest reactions of this type is with an acid to form a metal salt and water, and this is why
early efforts to combat potential corrosion were directed at reducing the acid gas production in
fire effluent.
However, it is not necessary for an acid to be present for oxidation to occur. If a metal is in
contact with an electrically conductive solution, the free ions of the solution can facilitate
corrosion of contacting metals by either reacting directly with the metal or by depolarizing the
area around the reacting metal. The rate of corrosion will depend on the area of metal
affected, the temperature, and on the magnitude of the difference between the electrode
potentials of the oxidizing and reducing couples. Metals higher in the electrochemical series
are more prone to corrosion.
Metal loss can cause many undesired effects. In buildings it can result in a weakening or
failure of structural elements. In electrical equipment it can cause a decrease in electrical
conductivity or ultimately the breaking of a circuit.
5.2.3 Moving parts becoming immobile
Fire effluent can cause moving parts in mechanical or electromechanical equipment to
become immobile, e.g. a ball bearing or parts in a circuit breaker. This may be because of the
deposition of sticky particulate matter or because of the formation of chemical corrosion
products between surfaces.
5.2.4 Bridging of conductor circuits
Fire effluent may contain conductive particulates, e.g. graphitic carbon or ionic species.
Metal corrosion also produces ionic species. These conductive species can bridge the small
gaps between the copper tracks on circuit boards causing undesired leakage currents. This
is of particular concern with digital telecommunications equipment.
5.2.5 Formation of a non-conducting layer on contact surfaces
This is a particular case of metal loss. Corrosion at the interface of a metal contact can result
in the formation of a layer of non-conducting material resulting in the loss of the circuit. This is
particularly likely if the contact is between dissimilar metals because they will form an
electrochemical cell when in contact with a conductive medium.

– 16 – IEC 60695-5-1:2021 RLV © IEC 2021
5.3 Factors affecting corrosivity
5.3.1 Introduction
The significant corrosion damage effects of fire effluent are assessed in terms of the rate of
functional impairment of the circuit or material affected. This impairment is dependent on a
number of factors. Some are related to the nature of the fire effluent, e.g.
– the chemical and physical nature and concentration of the fire effluent;
– interactions within the fire effluent such as smoke particulate ageing, agglomeration and
settling, condensation of liquid species, precipitation phenomena, and the absorption by
smoke particles of chemically reactive effluents.
These will in turn depend on the nature of the material being burned and on the physical fire
model being used.
Some factors are related to the corrosion environment, e.g.
– the physical and chemical nature of the affected circuits or materials;
– the prevailing conditions of temperature and relative humidity;
– the time of exposure;
– whether or not an electrical circuit is present and energized;
– post-exposure cleaning.
5.3.2 The nature of fire effluent
Many factors affect the production of fire effluent and its properties. A full description of such
properties is not possible, but the influence of several important variables is recognized.
Fire effluent is a consequence of both pyrolysis and combustion. Combustion may be
flaming or non-flaming, including smouldering, and these different modes of combustion may
produce quite different types of effluent. In pyrolysis and non-flaming combustion, volatiles
are evolved at elevated temperatures. When they mix with cool air, they condense to form
spherical droplets which appear as a light-coloured smoke aerosol. Flaming combustion
produces a black carbon-rich smoke in which the particles have a very irregular shape. The
smoke particles from flaming combustion are formed in the gas phase and in regions where
the oxygen concentrations are low enough to cause incomplete combustion. The most
abundant species in most fire effluents are carbon dioxide, water, carbon monoxide and
carbon-rich smoke.
However, many other chemicals may be present, including inorganic acids, organic acids and
ionic species. It is predominantly these last three types of material which cause fire effluent
to have a corrosive nature. The amounts of these materials which are present in fire effluent
will depend on the nature of the material being burnt and on the stage of the fire.
The heat flux on the test specimen influences how the material burns. It is good practice to
evaluate the effluent generated from materials at low levels of incident irradiance (e.g.
–2 –2 –2 –2
15 kW × m to 25 kW × m ) as well as at higher levels (e.g. 40 kW × m to 50 kW × m ).
In this way, the effects of the growth stages of a fire on the corrosive nature of the effluent
can be assessed.
The particle size distribution of smoke aerosols changes with time; smoke particles coagulate
as they age. Some properties also change with temperature so that the properties of aged, or
cold, smoke may be different from young, hot smoke. These factors may affect the way in
which smoke particles can cause short-circuits between electrical components.

5.3.3 The corrosion environment
The potential for corrosion damage can be reduced by protecting susceptible surfaces,
generally by using paint or lacquers. However, in many cases involving electrotechnical
equipment, this is not a practical solution.
The chemical nature of the exposed material will affect its susceptibility to corrosion
damage. Metals higher in the electrochemical series are more reactive. Those low in the
series such as gold and platinum are effectively inert. If dissimilar metals are in contact, one
of them will be particularly prone to corrosion because they make an electrochemical cell
when in contact with a conducting medium.
In many fire scenarios the affected materials will be at a high temperature, and temperature
has a major effect on the rate of corrosion. On average, the rate of a chemical reaction
doubles with a 10 °C K rise in temperature. The use of low heat release rate materials will
help to reduce fire temperatures and thus will reduce corrosive damage.
Relative humidity also affects corrosion reactions. Many reactions will not proceed in the
absence of water. Unfortunately, almost all fires produce water vapour as a major component
of the fire effluent so the relative humidity in the corrosion environment is likely to be high.
Also, if automatic water spray systems or fire fighters have been used, large quantities of
liquid water are likely to be present.
Two exposure times are involved. There is the time of exposure to the fire effluent when the
fire is occurring, and there is the subsequent exposure time to the prevailing conditions after
the fire has ceased. Both exposure times will affect the degree of corrosion damage. Some
reactions are auto-catalytic and therefore are initially slow but after a certain time will
progress rapidly. Also, some metals have a passive layer on their surface and again initial
reaction will be slow but when the passive layer has been removed, subsequent reaction may
be rapid.
A special problem with electrotechnical equipment is that exposed circuits may be energized.
This can cause electrochemical reactions that would not otherwise occur, and in some cases
can lead to destructive bridging or arcing phenomena.
6 Principles of corrosion damage measurement
6.1 Introduction
Corrosion damage measurement involves essentially two stages:
a) generation of the fire effluent;
b) assessment of the corrosive nature of the fire effluent.
However, each of these stages is complex and they both involve the selection of test
parameters from a wide range of possible choices.
6.2 Generation of the fire effluent
6.2.1 General
In a corrosion damage test, there are essentially two stages involved in the generation of the
fire effluent:
a) selection of the test specimen to be burned;
b) selection of an appropriate physical fire model relevant to the hazard being considered.

– 18 – IEC 60695-5-1:2021 RLV © IEC 2021
6.2.2 Selection of the test specimen to be burned
Different types of test specimens may be tested. In product testing, the test specimen is a
manufactured product. In simulated product testing, the test specimen is a representative
portion of a product. The test specimen may also be a basic material (solid or liquid) or a
composite of materials.
The nature of the test specimen is governed to a large extent by the scale of the test. Small-
scale fire tests are suited more to the testing of materials and small products or
representative samples of larger products. On a larger scale, whole products may be tested.
Given a choice, it is always preferable to select a test specimen that most closely reflects its
end use.
6.2.3 Selection of the physical fire model
It is important to consider the physical fire model or models most relevant to the hazard
being assessed, and to select tests which have fire models characteristics similar to those
being assessed (see IEC TS 60695-5-2).
6.3 Assessment of corrosive potential
6.3.1 General
It is desirable that the test procedure be designed in such a manner that the results are valid
for the application of an analysis of corrosion hazard, and also as part of an analysis of total
fire hazard. Work on the design of reaction-to-fire tests to ensure that results are valid for
assessment of hazard is in its early stages (see IEC 60695-1-1 for early guidance). The
guidance in this subclause will therefore be superseded as work progresses.
There are two approaches to the assessment of the corrosive potential of fire effluent. One
involves the exposure of a specific target to the effluent, and some measurement of
impairment. In this case, the target may be an actual product or it may be a simulated
product, e.g. a test circuit or a thin sheet of metal. The other approach is indirect and involves
the measurement of certain chemical properties of the fire effluent from which the corrosive
potential may, under defined conditions, be estimated or assessed. A summary of test
methods is given in Table 2.
6.3.2 Indirect assessment
Indirect assessment involves the dissolution of a known quantity of f
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