corrosion

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/