2. • Virtually no practical and engineering material is
stable. The rate of decay varies depending upon the
material and its environment.
• The human system cannot endure
– Temp above 50 C or below 20 C
– Pressures above or below our atmospheres
– Presence of harmful gases such as CO, H2S, and
H2.
• Thus, analogous to human system, engineering
materials also require protection like
– coatings, inhibitors, alloy addition, design
procedures, maintenance, inspection and re-
furnishing.
3. Corrosion is the disintegration of an engineered material
into its constituent atom due to chemical reactions with
its surroundings. In the most common use of the word,
this means electrochemical oxidation of metals in
reaction with an oxidant such as O2.
4. EFFECTS OF CORROSION
• Reduces Strength
• Life time is reduced
• Metallic properties are lost
• Wastage of metal
5. IMPORTANCE OF CORROSION
DATA
5 mpy Good corrosion
resistant material
5 to 50 mpy Low corrosion
resistant material
50 mpy Unsuitable as
constructional
material
18. STRESS CORROSION
BRITTLE CRACKS FORM AT
THE SITES OF STRESS.
FAILURE CAN BE FAST.
FAILURE CAN OCCUR AT
STRESS LOADS FAR BELOW
YIELD STRENGTH.
THREE CONDITIONS REQUIRED FOR MOST
COMMON KIND ARE -----
METAL UNDER
TENSILE
STRESS
DISSOLVED
OXYGEN
CHLORIDE
ION
21. Economic Impact of Corrosion
Annual estimated direct cost of corrosion
in the U.S. was approximately $276 billion
(approximately 3.2% of the US GDP.
Rust was the reason for the failure of
Mianus river bridge in 1983 and Silver
Bridge disaster of West Virginia in 1967
25. ACIVE CORROSION
PROTECTION
• The aim of active corrosion protection is to
influence the reactions which proceed during
corrosion, it being possible to control not only the
package contents and the corrosive agent but also
the reaction itself in such a manner that corrosion
is avoided.
.• Examples of such an approach are the
development of corrosion-resistant
alloys.
26. PERMANENT CORROSION
PROTECTION
• The purpose of permanent corrosion protection
methods is mainly to provide protection at the
place of use. The stresses presented by climatic,
biotic & chemical factors are relatively slight in
this situation.
• For example, in factories shed are
protected from extreme variations in
temperature, which is frequently the
cause of condensation.
27. What are the remedies or protective
measures
• Apply coatings on the metal
surface
• Removal of oxygen
• Control of pH
• Inhibitors
• Change of potential
But knowing beforehand the possible
effect of corrosion led to the development
of different softwares and models for
corrosion rate prediction
28. Various available softwares
Softwares have been developed by various organizations
but few of the well known software builders are :-
OHIO UNIVERSITY
ELECTRONIC CORROSION ENGINEERS
HONEYWELL
Multicorp and Freecorp are the products of Ohio
University
Honeywell has developed PREDICT-6.0 and PREDICTPIPE-
3.0
Two corrosion models have been developed by
ELECTRONIC CORROSION ENGINEERS and NORSOK
30. Effect of multiphase flow
(two- and three-phase flow)
Effect of temperature (1-100
C)
Effect of CO2 partial pressure
(0 – 2 MPa)
Effect of H2S content (0 – 1
MPa)
Effect of organic acids (0 –
10,000 ppm)
Effect of pH and brine
chemistry (pH3 – pH7)
Effect of steel type
Effect of inhibition by crude
oil and/or corrosion inhibitors
Magnitude and morphology of
localized attack
31. Processing window where the development of the corrosion rate
and surface scales can be tracked as a function of time
