different types of water are discussed which cause corrosion

1. Types of Corrosive
Water
Mian Muhammad Bilal
Muhammad Hamad Saeed

2.  Sea water
 Fresh water
 High purity water
 Brackish water
 Waste water
 Potable water
 Distilled water
 Cooling water

3.  Seawater or salt water is water from a sea or ocean.
 On average, seawater in the world's oceans has
a salinity of about 3.5%.
 This means that every kilogram (roughly one litre by
volume) of seawater has approximately 35 grams
(1.2 oz) of dissolved salts.

4.  Sea water can act as a good electrolyte and can cause
galvanic corrosion and crevice corrosion.
 Corrosion cause by sea water depend on oxygen
content, velocity, temperature and biological
organisms.

9.  Pitting and Cavitation
 Stress Corrosion

10.  Protection by painting
 Cathodic protection

11.  Inhibition
 Galvanic corrosion
 Using corrosion resitant alloys
Metals and Alloys that are normally use in seawater
are
Titanium, copper nickel alloys and nickel chromium
molybdenum alloys.

12.  Corrosivity in fresh water varies depending upon
oxygen content, hardness, chloride content.
 Depending upon the minerals dissolved fresh water
can be
 Hard water
 Soft water

13.  Soft waters are usually more corrosive than hard water.
 Cast iron, galvanized steel brass, aluminium are most
widely used materials for handling fresh water.

14.  As the purity of water increases corrosion resistance
increases.
 It is normally use as a heat transfer medium.
 Intergranular attack and cracking of solution
quenched stainless steels and alloys occur in high
purity water containing oxygen.

15.  WASTEWATER is the fancy term applied to water
that is contaminated by human activity such as
bathing, dishwashing and flushing the toilet or it
may be of industrial waste.
 Globally, two million tonnes of sewage, industrial
and agricultural waste is discharged into the
world's waterways.

17.  While traveling through sewer lines, the
wastewater can become anaerobic or septic as a
result of the metabolic processes of microbes
commonly found in wastewater
 Under anaerobic conditions, specific sulfate-
reducing bacteria thrive. These microbes generate
hydrogen sulfide (H2S) as a byproduct of their
respiration

20.  H2S has a low solubility in wastewater and when it
escapes from the wastewater and moves into the
air it is easily recognized by its characteristic
offensive, rotten-egg odor.
 H2S can also be responsible for severe corrosion
problems and toxic
conditions. So the
corrosion invovled is
Biological corrosion.

22.  Brackish water is water that has more salinity than fresh
water, but not as much as seawater. It may result from
mixing of seawater with fresh water.

23.  Brackish water contains between 1 and 2.5% sodium
chloride, either from natural sources around otherwise
fresh water or by dilution of seawater.
 Brackish water differs from open seawater in certain
other respects. The biological activity, for example, can
be significantly modified by higher concentrations of
nutrients.

24.  Any compound capable of donating free chlorine ions
(Cl -) to an aqueous (water-based) solution has the
potential for causing failure in stainless steels. The
chlorine ion is extremely electronegative, and
therefore very reactive with certain compounds and
elements.

25.  Chloride attack of stainless steel is spreading out
evenly as rust does. So thin tubes and pipes will not
necessarily last much longer than thick ones before
failing due to chloride induced corrosion.

28.  The observed cracking of monel alloy bolt in service is
due to MIC by SRB.
 Inter granular corrosion attack on the grain
boundaries was by MIC.
 The only conceivable source of sulfide in this case is
bacterial activity of Sulfate Reducing Bacteria (SRB).
 The sulfides can cause breakdown of the passive film
layer on the Monel alloy.
 Thus making it susceptible to intergranular corrosion
by chlorides.