ISO/TR 4340:2022

TECHNICAL ISO/TR
REPORT 4340
First edition
2022-06
Water aggressiveness evaluation and
optimized lining choice
Évaluation de l’agressivité de l’eau et choix optimal des revêtements
intérieurs
Reference number
© ISO 2022
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ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Water aggressiveness evaluation . 2
4.1 Normal internal corrosion mechanics . 2
4.2 Internal protection of ductile iron pipe . 2
4.3 Water aggressiveness evaluation for ductile iron pipe system. 3
4.4 Main corrosive aggressive factors . 3
4.5 Water evaluation indicators and their trigger value . 4
4.5.1 Langelier saturation index (LSI) . 5
4.5.2 Ryznar stability index (RSI) . . 5
4.5.3 Calcium carbonate precipitation potential (CCPP) . 5
4.5.4 Larson ratio (LR) . 6
4.5.5 Aggressive index (AI) . 6
4.5.6 Evaluation chart . 6
5 Sampling and testing .7
5.1 Sampling . 7
5.2 Testing . 8
6 Optimized lining choice based on water evaluation . 8
7 Steps for water aggressiveness evaluation and optimized lining choice .8
Annex A (informative) pH . 9
s
Annex B (informative) Relevant test standards .12
Annex C (informative) Type and characteristics of water-related concrete corrosion .18
Bibliography .19
iii
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
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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 documents 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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 5, Ferrous metal pipes and metallic fittings,
Subcommittee SC 2, Cast iron pipes, fittings and their joints.
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.
iv
TECHNICAL REPORT ISO/TR 4340:2022(E)
Water aggressiveness evaluation and optimized lining
choice
1 Scope
This document provides details about the aggressiveness factors, evaluation indicators of raw water, or
inlet water of ductile iron pipe system and relevant lining information applicable to ductile iron pipes,
fittings and accessories used in water mains and distribution system.
This document is intended to serve as a tool for estimating the properties of certain water and their
effect on internal linings of ductile iron pipes, fittings and accessories used in water mains and
distribution system which are specified in ISO 2531, ISO 16631 and can be used to decide the most
appropriate protective measures to ensure long term durability of pipeline.
It is not always possible to definitively determine the aggressive parameters of certain water, and fully
considered by limited test and evaluation. Therefore, the history information of the evaluated water,
experiences of local water works can be taken for reference.
The aggressiveness evaluation of water can be carried out before determining the internal lining
materials of certain pipeline, and the evaluation and relevant tests can be done by qualified laboratories
and engineers.
Water that leads to high-level scaling in the pipeline is believed aggressive.
Drainage and waste water are not in the scope of this document, the internal protection of drainage and
waste water can be recommended by pipe suppliers.
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.
ISO 2531, Ductile iron pipes, fittings, accessories and their joints for water applications
ISO 16631, Ductile iron pipes, fittings, accessories and their joints compatible with plastic (PVC or PE)
piping systems, for water applications and for plastic pipeline connections, repair and replacement
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 2531 and ISO 16631 and the
following 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
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
scaling
dissolvable salts, residues of water pipeline inner surface reaction and other solids deposit on the inner
surface of pipeline components, which will reduce the cross-sectional area and increase the head loss
Note 1 to entry: Scaling is sometimes also harmful to water quality and pipeline service life. The scaling process
is normally related to the water chemical stability, temperature, flow rate, inner surface roughness of the pipeline
component.
3.2
corrosive water
type of water which attacks metal component (pipe, fitting, accessories) without an internal coating
Note 1 to entry: The chemical reactions produce ferrous and then ferric hydroxides, forming nodules and
tuberculation, which eventually reduce the component’s cross-sectional area and significantly increase head
loss, reduce the service life of metal pipeline components.
3.3
water aggressiveness
propensity to react with materials containing calcium such as hydraulic binders
Note 1 to entry: Depending on the chemical analysis, mineral content, pH and temperature of the water, three
cases can occur:
— Water in calco-carbonic equilibrium does not attack or deposit calcium carbonate at a given temperature.
— Scaling water tends to deposit calcium salts (carbonates, etc.) on the pipeline components’ inner surface.
— Aggressive water can attack certain components of cement mortar containing calcium (lime, calcium silicate
and calcium silicoaluminate).
Note 2 to entry: Normally, ductile iron pipe components are supplied with linings, and cement mortar linings
are the standard internal protection, so aggressive water and water aggressiveness are mostly used in this
document. But the reaction with uncoated metal surface is also considered and described in some parts of this
document.
4 Water aggressiveness evaluation
4.1 Normal internal corrosion mechanics
Internal corrosion mechanics of ferrous pipeline system have been studied for decades, according to
the state of art, major pipeline internal corrosion problems can be traced to the stability of calcium
magnesium carbonate system and iron system in the water. The status and the change of stability of
these systems can lead to the deposition and dissolvement of carbonate and ferrous compound, which
is the major reason of lining failure, red water, yellow water, scaling and related secondary corrosion.
The stability of calcium magnesium carbonate system and iron system are complex systemic ion
balance problem related to multiple positive and negative ions, and highly related to water temperature.
Considering those factors one by one is not a good way to get comprehensive information of the water
aggressiveness, those factors are a united system and can be considered systematically.
Many indexes and indicators are concluded to evaluate the aggressiveness or stability of water.
4.2 Internal protection of ductile iron pipe
Ductile iron pipes are normally supplied with internal linings. There can be some special applications
without internal linings. Linings are believed an effective way to protect the pipe when they are used
appropriately. It is possible to categorize all existing linings as isolation barriers (polymeric linings),
active protection (cement mortar lining), or their combination (cement mortar lining+seal coat). Cement
mortar linings are standard internal protection of ductile iron pipes, and currently, most of ductile iron
pipes are lined by cement mortar lining.
Other linings or internal protections can exist or can be developed as the updating pursue of water
quality and pipeline service time.
Suitable lining choice based on water aggressiveness evaluation is beneficial to ensure the durability of
lining protection in the long term and reduce the negative effect on water quality.
4.3 Water aggressiveness evaluation for ductile iron pipe system
Ductile iron pipes and fittings are used at any part of the water distribution system. They will influence
other pipeline sections by the flowing water and be influenced as well. The interaction of ductile iron
pipe and water can be considered based on the stability of calcium magnesium carbonate system and
iron system. The interaction of water and cement mortar can also be considered at the same time.
In this document, multiple indicators with comprehensive consideration of aggressive factors based
on calcium magnesium carbonate system, iron system, and also the interaction of water and cement
mortar material are used to evaluate the aggressiveness of water.
4.4 Main corrosive aggressive factors
4.4.1 The pH value: the pH value of water is a measure of the concentration of the hydrogen ion
+ +
concentration (H or H O ). The pH scale ranges from 0 to 14. Values less than 7,0 are considered
acidic, values greater than 7,0 are considered alkaline, and 7,0 is considered neutral. Drinking water pH
values typically range from 6,0 to 10. At higher pH values, there is less of a tendency for metal surfaces
in contact with drinking water to dissolve and dissociate, which is why pH adjustment is a common
component of an effective corrosion control treatment strategy. Maintaining a consistent target pH
throughout the distribution system is always critical to minimizing lead and copper levels at the tap
and minimizing discoloured-water complaints, even if other corrosion control methods are employed.
Another important consideration with regard to pH is its impact on other water quality parameters.
It plays a significant role in the carbonate balance in that it impacts buffer capacity and dissolved
inorganic carbon (DIC) concentrations. It also influences other corrosion-related parameters, such as
oxidation–reduction potential (ORP) and corrosion inhibitor effectiveness.
4.4.2 Alkalinity: alkalinity is the capacity of water to neutralize acid. It is the sum of carbonate
2– – –
(CO ), bicarbonate (HCO ), and hydroxide (OH ) anions and is typically reported as milligrams per
3 3
litre as calcium carbonate (mg/L as CaCO ). Waters with high alkalinities tend to have high buffering
capacities or a strong ability to resist changes in pH. Low-alkalinity waters are less able to neutralize
acids or resist changes in pH.
4.4.3 Total dissolved solids/ionic strength: total dissolved solids (TDS) can have an impact
on corrosion, though the effect can be less than other corrosion-related parameters. High TDS
+ 2+ 2+ – 2–
concentrations are generally associated with high concentrations of ions (e.g. Na , Ca , Mg , Cl , CO ,
2–
SO ) that increase the conductivity of the water. Corrosion is an electrochemical reaction in which
electrons from the anodic surface are transferred to the cathodic surface. The increased conductivity
resulting from high TDS concentrations increases the ability of the water to complete the electro
chemical circuit and conduct a corrosive current.
If sulfate and chloride are major anionic contributors to the TDS, the TDS is likely to show increased
corrosivity toward iron-based materials. If the TDS is composed primarily of bicarbonate and hardness
ions, the water will probably not be corrosive toward iron based or cementitious materials but can
probably be highly corrosive toward copper. Low-TDS waters can also be corrosive and increase lead
solubility. Low-TDS waters often have a strong tendency to dissolve (corrode) materials with which
they are in contact in order to reach electro neutrality. Uniform corrosion is an electrochemical process
in which the water solution in contact with the cathode provides the chemicals to accept the electrons
donated by the pipe wall. The pipe wall, acting as an anode, then releases the oxidized metal ion to
the water. Water has a limited capacity to accept dissolved species. Thus, although high-TDS waters
have many electron receptors, low-TDS waters have the ability to accept a large number of anions and
cations, resulting in a subsequent dissolution of existing pipe scales and corrosion of pipe surfaces.
TDS is a surrogate for the ionic strength of a solution. The ionic strength is a measure of the force of the
electrostatic field caused by the presence of ions in a solution. More simply, the presence of anions and
cations in solution increases the conductivity of the solution and can increase corrosion unless offset
by passivating layers on the pipe surface. It is possible to determine the ionic strength as shown in
Formula (1).
-5
I=2,5×10 ×TDS (1)
where: I = ionic strength; TDS = total dissolved solids concentration, in mg/L.
4.4.4 Dissolved inorganic carbon: DIC is the sum of all DIC-containing species and is one of the most
critical parameters for controlling internal corrosion. It includes dissolved aqueous carbon dioxide
– 2–
gas (CO or H CO ), bicarbonate ion (HCO ), and carbonate ion (CO ) in a particular water, and DIC
2 2 3 3 3
is usually expressed as milligrams per litre of carbon (mg/L as C) or milligrams per litre of calcium
carbonate (mg/L as CaCO ). Although DIC and alkalinity are similar, they are not the same water quality
parameter. DIC varies according to water temperature, pH, ionic strength, and alkalinity.
4.4.5 Hardness: hardness is a characteristic that represents the presence of dissolved multi-valence
cations, primarily calcium and magnesium, in water and is reported as an equivalent concentration of
calcium carbonate (CaCO ). Hardness can be taken into consideration when corrosion control is selected
and implemented because it can create scaling problems within the treatment plant, distribution
system infrastructure, and customer plumbing. In this regard, hardness is an important parameter to
be considered in developing a corrosion control program and evaluating the amount of pH adjustment
that is permissible without causing scale problems.
4.4.6 Dissolved oxygen: dissolved oxygen (DO) can play important roles in both corrosion reactions
and metals release. Oxygen can serve as an electron acceptor in the corrosion cell, allowing for metal
oxidation at the pipe surface and release of ionized metal species into the water. Thus, new metal
surfaces that are exposed to water containing DO will corrode faster compared to anaerobic water.
4.4.7 Oxidation–reduction potential: ORP, also frequently referred to as redox potential, is a
measure of water’s capability to oxidize and is reported as electrical potential (volts, V, or millivolts,
mV).
4.4.8 Metal ions and anions: it is possible to indicate metals in water as total metal and dissolved
2+ 2+ 3+ 2+ 3+
metal, dissolved metal ions such as: Ca , Mg , Fe , Mn , Al . Their dissolvement balance affect
the water quality and scale formation. Some metal ions are regularly monitored deal to their effect
on human health such as lead, they are normally limited in local water quality specifications. Some
anions are highly related to the crystallization corrosion of concrete, their mechanisms are introduced
in Annex C.
4.5 Water evaluation indicators and their trigger value
Water aggressiveness is evaluated by comprehensive indicators. Normally, two equilibrium systems are
considered for ductile iron pipe internal protection: iron equilibrium system and carbonate equilibrium.
As ductile iron pipes are normally supplied with cement mortar linings, the aggressiveness of water to
cement material can be evaluated.
In this document, five indicators can be used to evaluate the water aggressiveness. Their calculation
and trigger value are showed in 4.5.1, 4.5.2, 4.5.3, 4.5.4, and 4.5.5. Other water evaluation indicators or
scaling tendency indicators are possible.
4.5.1 Langelier saturation index (LSI)
LSI=pH-pH (2)
s
where:
LSI is the Langelier saturation index;
pH is the pH value;
pH is the saturation pH (the calculation of pH is shown in Annex A).
s s
The indications for the LSI are based on the following values:
LSI <0 water is under saturated with respect to calcium carbonate and has a tendency to remove
existing calcium carbonate protective coatings in pipelines;
LSI = 0 water is considered to be neutral, neither scale-forming nor scale removing;
LSI >0 water is supersaturated with respect to calcium carbonate and scale forming can occur.
4.5.2 Ryznar stability index (RSI)
RSI=2pH -pH (3)
s
where:
RSI is the Ryznar stability index;
pH is the pH value;
pH is the saturation pH (the calculation of pH is shown in Annex A).
s s
RSI is normally used together with LSI; they are based on the same thermodynamic hypothesis.
RSI <5,0 heavy scale will form;
RSI = 5,0~6,0 light scale;
RSI = 6,0~7,0 little scale or corrosion;
RSI = 7,0~7,5 corrosion significant;
RSI = 7,5~9,0 heavy corrosion;
RSI >9,0 corrosion intolerable.
4.5.3 Calcium carbonate precipitation potential (CCPP)
The CCPP predicts both tendencies to precipitate or to dissolve CaCO and quantity that can be
precipitated or dissolved. It is also known as calcium carbonate precipitation capacity (CCPC).
The CCPP is defined as the quantity of CaCO that theoretically precipitate from oversaturated waters
or dissolved by undersaturated waters during equilibration.
2+ 2+
CCPP=100*([ Ca ] —[Ca ] ) (4)
i eq
Unit: mg-CaCO /L.
where:
2+ 2+
[Ca ] —[Ca ] concentration of water sample, in mol/L;
i
2+ 2+
[Ca ] —[Ca ] concentration of water in CaCO equilibrium status.
eq 3
CCPP = 0~4 no scaling or little scale CCPP = 0~-5 slight corrosion
CCPP = 4~10 light scale CCPP = -5~-10 corrosion
CCPP = 10~15 heavy scale CCPP ≤ -10 heavy corrosion
CCPP ≥ 15 very heavy scale
CCPP is not suitable for hand calculation. It can be calculated by software or determined by experiments.
4.5.4 Larson ratio (LR)
−−2
     
LR= Cl + SO / HCO (5)
() −
     
Unit: mol/L
LR shows the effect of anions in water, which is significantly related to iron-equilibrium and
aggressiveness to cement materials.
LR <0,5 non corrosive water;
LR = 0,5~1 slight corrosion;
LR >1 corrosive, bigger value, heavier corrosive.
4.5.5 Aggressive index (AI)
AI =pH+lg (Ca*Alk) (6)
where:
Ca is the hardness, in mg-CaCO /L;
Alk is the total alkali, in mg-CaCO /L.
AI shows the aggressiveness to cement material.
AI <10 heavy aggressive;
AI = 10~12 aggressive;
AI >12 not aggressive.
4.5.6 Evaluation chart
The following chart can be used to evaluate the aggressiveness of certain water sample. The way to
evaluate water stability of certain water sample is shown in Table 1.
...