THE NATURE OF WATER AND ITS EFFECTS ON FLUID NETWORKS
Compiled by Fahri AKALIN, grad. m arine engineer, 1970
[email protected] or [email protected]
Water is the most widely used resource in mankind’s total activities. It is always important to recognize the presence
and effects of naturally occurring calcium and magnesium carbonates (ionic compounds), other salts and micro
organisms present in sources of water.
Salts present in fluid networks will adhere to internal walls due to the natural presence of electric charges in the water
and molecular properties found in their crystal structure. Under certain pressure and temperature conditions, this scale
encrustation will inevitably increase and create a thick layer of calcium and magnesium resulting in costly economic loses
and causing serious production inefficiencies.
Scaling - Its a natural process but can be prevented
Hard water: A matter of Ions
Practically all-industrial sectors use water in production for heating or cooling application. However, not all such users are
aware of the effects of certain elements in matters that can cause operational problems. One of the most important
impurities to take into consideration is water hardness and its effects on industrial systems.
Water hardness refers to the dissolved ions in water sources (soli d particles with a net electric charge). Specifically,
calcium [Ca 2+] and magnesium ions [Mg 2+] are the ions whose net charges are positive (cations), as calcareous rocks
gradually begin to disintegrate, various sediments caused by the erosion of the rocks are retained in ground water. It is
these properties contained in the sediment in the ground water that cause significant scaling problems.
Cations, with their positive charges, are balanced with the anions presence (negative net charge), producing the m ost
2important products, bicarbonates [HCO3 ] and carbonates [CO3 ]. Those anions originate from the natural dissolved
carbon dioxide [CO2] in water.
Ions, with opposite net charges, do interact with a great number of chemical phenomena such as crystallization
(calcareous scales origin) and electrochemical oxidation reactions (galvanic corrosion origin). Both processes occur
spontaneously always with saline compounds, water, dissolved oxygen, acidic media. Its effect on metal surfaces is to
cause the formation of scale as well as start the process of gradual corrosion of metal surfaces.
Crystallization: The origin of scaling
Ions, with opposite charges, join each other (due to the natural electrostatic forces) ionic bonds following a regular and
ordained scheme displayed in a crystal form due to the presence of solid and consistent salts. Ionic bonding results from
the net electrostatic attraction force between net opposite charged ions (anions & cations).
Crystallization occurs under very common condit ions in a wide variety of applications :
 Super saturation of dissolved solids (bigger concentrations of dissolved ions than the solution can effectively
absorb).

Initial Nucleation due to the solutions ions combining with other ions that do not belong to the liquid phase, (i.e.
metallic surfaces in contact with a liquid phase).
 Crystal growth as a consequence of ionic bonding with other precipitated salts.

Other factors such as sudden temperature increases, turbulence in the system , condition of the surface in
contact with the solution, and other impurities present can affect the solvents balance under such conditions.
Crystallization forms: Calcite and Aragonite
Dissolved ions crystallization, formed under the above mentioned conditions produce ionic compounds like calcium and
magnesium salts . These are very hard substances and readily adhere to pipes and machinery surfaces, especially in
heat transfer areas.
Scaling is fundamentally formed in greatest proportion by calcite, and, to a lesser degree by aragonite.
Both compounds are calcium carbonates with an identical chemical structure, but with different crystalline
structures. Calcite has a significant scale-forming capacity in comparison to that of aragonite.
Scaling
Unless scale build-up is controlled and ultimately eliminated, calcium and magnesium carbonates will create a constant
and corrosive presence by forming a thick crust, which is mechanically hard to remove and reduces the thermal
efficiency in both heating and cooling applications. Not only does this scaling and corrosion create inefficiency in pipes, it
also results in excessive energy consumption in cooling systems creating the possibility of failures due to overheated
machinery.
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What is corrosion?
Corrosion is defined as a metallic material reduction as a consequence of an environment chemical attack. Whenever
the origin of the corrosion is caused by a chemical reaction, the speed at which it takes place will depend in some degree
on the temperature, the fluid salinity, and the metals properties in question.
The corrosion that habitually affects pipes and machineries is the wet corrosion, an electrochemical process that needs
three conditions to be developed simultaneously:
1- anode,
2- cathode and
3- electrolyte (electrically aqueous solution)
If one is lacking, the corrosion stops. These three elements constitute what is known as a galvanic cell or
electrochemistry.
The corrosion occurs in the anode areas, while the cathode ones always remain unaffected. The corrosion will be
proportional to the electrolytes conductivity. In a higher concentrated saline solution, thus having a higher conductivity,
any corrosive process will be increased in activity and in speed. Fresh water will be a slower driver, thus the corrosion
will be slower and less active in relation to the first case.
Usual corrosion cause s
Metallic surfaces habitually form prone areas to be corroded (anode areas) due to several factors, among them :

Metal deformation: Metal crystal structure changes caused by heat, abrupt thermal differences, mechanical
effects, cracks and fissures from fatigue, etc. The deformed sections corrode (anode area) in preference to the
intact areas that are not corroded. The galvanic current taken place between both is increased or decreased
proportionally according to the fluids salinity that surrounds them.

Contact between two different metals: Due to the differences in their potentials, the most active metal will
suffer corrosion in preference to the more noble metal that stays intact. The galvanic current is increased or
decreased proportionally according to the fluid salinity (electrolyte)

Evans Effect Corrosion (scales influence): Sediments on a metallic surface creates an anode area
exactly under the deposit, where the oxygen concentration is minor in comparison with the peripheral one.
Differences in the oxygen concentrations originate with great ease in the presence of salts scales.
Scales, and salinity level are corrosion facilitators
As much as the dissolved salts present in the fluid flow, as the solid scale formation on a metallic surfaces, these are
factors that increase the speed and intensity of the corrosive processes , and thus constitute another central axis, where
the technology effectivel y aims. When the fluid salinity decreases, natural scaling in pipes is stopped or eliminated in
circuits and machineries,
Scale and Corrosion caused by the presence of salts in water
In a water network system without water treatment technology, salts create a progressive scale forming process
affecting all metallic conduits. Salts are also the cause of a process, that is commonly known as corrosion, a destructive
and spontaneous electro-chemical reaction that we know aggressively affects the greater part of all metals commonly
used in industry and production activities.
Without an effective water treatment system, scale formation is inevitable and it can severely jeopardize the
water network and the effective functioning of machinery and related parts:
 Rapid increase in layers of scale will cause a decrease in the flow of water ultimately resulting in a total
paralysis of the water flow.

The presence of irreversible corrosion on the entire metallic surface in the network is completely d etrimental to
the system.
 Replacement of a complete section of piping is often necessary due to scale encrustation or corrosion in a
water distribution system.

Machinery components are also frequently replaced due to severe scale formatio n and corrosion.

Heat transfer loses of between 40% and 90 % can be caused by the thermal isolation of scale formation
in distillers, heat exchangers, cooling towers, condensers and boilers .
Hot water transportation pipe-section (Pipe dia. 5 inches)
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