CORROSION“ A Simple view on a complex matter”
• 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 50C or below 20C – 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.
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.
EFFECTS OF CORROSION• Reduces Strength
• Life time is reduced
• Metallic properties are lost
• Wastage of metal
IMPORTANCE OF CORROSION DATA
5 mpy Good corrosion resistant material
5 to 50 mpy Low corrosion resistant material
50 mpy Unsuitable as constructional material
EXAMPLES OF CORROSION
MICROBAL CORROSIO
N
GALVANIZED SURFACE
GOLD NUGGETS
RUST
CHEMICAL EQUATION OF CORROSION
Fe2O3.XH2
O
Corrosion in teeth fillings
TYPES OF CORROSION UNIFORM
GALVANIC
PITTING
STRESS
MICROBIAL
EROSION
UNIFORM CORROSION CAN BE A GOOD OR A BAD THING.
CORROSION OCCURS EVENLY OVER THE SURFACE. OXIDE LAYER CAN BE VERY TOUGH – MAGNETITE.
FE3O4
GALVANIC CORROSION o CHEMICAL
REACTIONS.
o ELECTRONS REMOVED FROM ONE REACTANT TRAVEL THROUGH AN EXTERNAL CIRCUIT.
oMETERIAL TENDS TO DISAPPEAR.
Microbiological corrosion
Galvanic corrosion
Crevice Corrosion
PITTING CORROSION
STRESS CORROSIONBRITTLE 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
ERROSION CORROSION• FLOW REMOVES PROTECTIVE
LAYER.
• NEW POTECTIVE LAYER FORMS USING UP METAL.
MICROBIAL CORROSION
SIMILAR TO PITTING CORROSION.
BACTERIA IN WATER.
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
PREVENTIONS OF CORROSION
ACIVE CORROSION PROTECTION
PERMANENT CORROSION PROTECTION
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.
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.
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
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 UniversityHoneywell has developed PREDICT-6.0 and PREDICTPIPE-3.0Two corrosion models have been developed by ELECTRONIC CORROSION ENGINEERS and NORSOK
Multicorp v4.2
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
Processing window where the development of the corrosion rate and surface scales can be tracked as a function of time
Batch run results
Line run results
Norsok m-506
This model calculates the CO2 corrosion rate on the basis of given temperature, pH , CO2 partial pressure and shear stress
Electronic Corrosion Engineers
• It consists of a tubing project and a pipeline project
Created & Edited by –
ABHIJEET DASH
REFERENCES• http://www.corrosioncenter.ohiou.edu/software/multi
corp/
• https://www.honeywellprocess.com/en-US/explore/products/advanced-applications/asset-management/corrosion-prediction-and-assessment/Pages/predict-6.0.aspx
• https://www.honeywellprocess.com/en-US/explore/products/advanced-applications/asset-management/corrosion-prediction-and-assessment/Pages/predictpipe-3-0.aspx
• http://www.corrosionhelp.com/services.htm#Electrochemical Analysis
• http://www.corrosionservice.com/
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