Corrosion Science

TALAT Lecture 1252- Corrosion and Corrosion Protection
1252.01.02 Corrosion Types ....................................................................................4
(a) General corrosion.............................................................................................5
(b) Crevice corrosion.............................................................................................6
(c) Poultice corrosion ............................................................................................7
(d) Fretting corrosion (also called traffic marking)...............................................7
(e) Stress corrosion................................................................................................8
(f) Galvanic Corrosion ..........................................................................................9
(g) Pitting Corrosion............................................................................................10
(h) Intergranular corrosion and exfoliation .........................................................11
1252.02 Electrochemistry and Aluminium...........................................................11
1252.02.01 Introduction .........................................................................................11
1252.02.02 Kinetic Reactivity................................................................................12
1252.02.03 The Electrochemical Circuit ...............................................................13
1252.02.04 Aluminium as a Cathode.....................................................................13
1252.02.05 Aluminium as an Anode......................................................................14
1252.02.06 Summary of Electrolytic Corrosion .

Metallurgical Factors Affecting Corrosion in Petroleum and Chemical Industries
Abstract:
Humans have most likely been trying to understand and control corrosion for as long as
they have been using metal objects. With a few exceptions, metals are unstable in ordinary
aqueous environments. Certain environments offer opportunities for these metals to
combine chemically with elements to form compounds and return to their lower energy
levels. Corrosion is the primary means by which metals deteriorate. Most metals corrode on
contact with water (and moisture in the air), acids, bases, salts, oils, aggressive metal
polishes, and other solid and liquid chemicals. Metals will also corrode when exposed to
gaseous materials like acid vapors, formaldehyde gas, ammonia gas, and sulfur containing
gases. The production of oil and gas, its transportation and refining, and its subsequent use
as fuel and raw materials for chemicals constitute a complex and demanding process.
Various problems are encountered in this process, and corrosion is the major one. Since
metals are the principal material suffering corrosive deterioration, it is important to develop
a background in the principles of metallurgy to fully understand corrosion. The control of
corrosion through the use of coatings, metallurgy, nonmetallic materials for constructions
cathodic protection and other methods has evolved into a science in its own right and has
created industries devoted solely to corrosion control. Metallurgical factors that affect
corrosion are chemical composition, material structure, grain boundaries, alloying elements,
mechanical properties, heat treatment, surface coating, welding and manufacturing
conditions. Understanding these factors are of great importance to decrease and control
corrosion problem in many industrial applications.

This updated definitive publication on inorganic zinc silicate coatings is directed at the needs of all users of this remarkable protective coating. The publication features a compilation of  papers published in Australia between 1937 and 2011. The papers focus on all aspects of inorganic zinc silicate protective coatings, providing a comprehensive examination of the history, development, chemistry and uses. It includes papers dealing with cure, breakdown mechanisms, microstructure and comparisons with multi-coat systems, organic zinc, metal spray and galvanizing. An overview provides a useful summary of each of the papers. A comprehensive reference book for engineers, paint chemists, specifiers, superintendents and maintenance personnel.

1. Uniform (general) corrosion
2. Galvanic (two–metal) corrosion
3. Thermogalvanic corrosion
4. Crevice corrosion (including deposit corrosion)
5. Pitting, pitting corrosion
6. Selective attack, selective leaching (de–alloying)
7. Intergranular corrosion (including exfoliation)
8. Erosion corrosion
9. Cavitation corrosion
10. Fretting corrosion
11. Stress corrosion cracking
12. Corrosion fatigue

A study of the effect of allium cepa extract as an inhibitor on mild steel corrosion in 0.5M HCl was made at ambient temperature. The experiments were performed with the weight loss/corrosion rate and potentiostatic polarization measurement techniques. Polarization measurement was performed using a potentiostat (Autolab PGSTAT 30 ECO CHIMIE) interfaced with a computer for data acquisition and analysis. Effective corrosion inhibition of the extract on the steel test specimens in the different concentrations of HCl used was achieved as indicated with the results obtained. There was increasing inhibition performance with increasing concentration of the extract inhibitor. The best inhibition performances were achieved at the lower exposure times for all the extract concentrations used in the 0.5 M HCl. A good correlation of results was obtained for the gravimetric and polarization experiments. A mixed type inhibitor is indicated with the results of ba and bc.

Concrete is a porous material. The size and distribution of pores in concrete varies, depending upon the quality of compaction, the materials, the water-to-cement ratio and the degree of hydration. Many of these pores are inter-connected creating larger and more complex pore systems. Water can penetrate this network and cause deterioration of the concrete structure. Silanes have been generally used in the past to help protect reinforced concrete exposed to an aggressive environment. The treatment works as a pore liner, thus ...

Abstract
The surface characteristics and corrosion behaviour of the AZ31 magnesium alloy exposed to a high relative humidity (RH) atmosphere were investigated. During the first 15 days of humidity test at 98% RH and 50 °C, a significant increase of magnesium carbonate and a decrease of magnesium oxide were detected on the surface film by XPS; after this stage, increased exposure times did not produce substantial changes on the relative amounts of these compounds. The surface film of commercially pure magnesium, also examined for comparison purposes, revealed more magnesium carbonate and less magnesium oxide compared with the AZ31 alloy. Unlike the AZ31 alloy, the surface of pure Mg disclosed almost complete substitution of MgO by magnesium carbonate after 30 days of exposure time. Mass gain values of tested specimens and scanning electron microscope characterisation of corroded surfaces indicated lower corrosion susceptibility of the AZ31 alloy compared with the commercially pure Mg, suggesting superior chemical stability of the oxide/hydroxide film formed over the magnesium–aluminium alloy surface. XPS and energy dispersive X-ray (EDX) analyses did not revealed any substantial enrichment of aluminium in the corrosion products film on the AZ31 alloy after 30 days of testing. Copyright © 2008 John Wiley & Sons, Ltd.

This research reports the consequences of mass loss estimations by utilizing of oxygen scavengers in boilers to limit the consumption rate of carbon steel tubes. The consumption rate information was chosen from the literature as function of temperature, pressure, and inhibitors level. Consumption rate increased with increasing in temperature and pressure, and diminished with inhibitor level. Hydroquinone, ascorbic acid, and ethanolamine were utilized as consumption inhibitors. The present work is focused on deciding the artificial neural network (ANN) and mathematical formulas so as to increase great expectation properties. Five scientific models and five ANN display structures were recommended. Computer aided program was utilized for building up these models. The outcomes demonstrate that the polynomial mathematical model and multi-layer discernment can precisely anticipate the deliberate information with high relationship coefficients. Multi-Layer Perceptions (MLP) 3:3-4-1:1 was the best model over than the others with higher correlation coefficient.

This experimental field study interrupted the protection current offered by Impressed Current Cathodic Protection (ICCP) to ten in-service reinforced concrete structures. The study aimed to identify the long-term effects of ICCP after it was recognised that some of the systems are now reaching the end of their design life and require a significant level of maintenance. It was found that after five or more years of ICCP, the steel remained passive for at least 24 months after interrupting the protection current despite chloride contamination that would represent a corrosion risk.

In this study, we have investigated possible role as iron corrosion inhibitor of four benzotriazole derivatives, BTA, BTA-C1, BTA-C4, BTA-C6, using DFT calculations at B3LYP/6-311G** level of theory. For this purpose, we have determined some structural and electronic parameters such as HOMO and LUMO orbital energies, energy gap, electron affinity, ionization potential, hardness, softness, absolute electronega-tivity, chemical potential, electrophilicity index, fractions of electrons transferred and back donation, logP, molecular surface area, polar surface area, molecular volume, molar refractivity and have compared with experimental literature results. We have also computed and discussed the interaction energy of the inhibitors with iron surface. The calculated parameters are closely related to the inhibition efficiencies, and have compared with experimental literature values using linear regression analysis to determine the most effective parameters on inhibition efficiency.

This work describes the inhibition effect of different concentration of an aqueous extracted of Pe-ganum harmala seed on the corrosion of carbon steel in 1 M H2SO4 solution using potentiostatic polarization techniques at the temperature range (298-328) K. The result showed that the inhibition efficiency increased with increasing of extract inhibitor concentration and temperature. The adsorption of inhibitor on carbon steel surface was fit into Langmuir adsorption isotherm. Kinetic and thermodynamic parameters governing the corrosion and the adsorption process were calculated and discussed.

Inhibition of corrosion of nickel–aluminum bronze alloy (NAB) by use
of 4-amino-5-phenyl-4H-1,2,4-triazole-3-thiol (APTT) was investigated by monitoring
weight loss and open-circuit potentials (OCP), and by use of electrochemical
impedance spectroscopy (EIS). Quantum chemical data were calculated by use of
the density functional theory (DFT) model. Results showed that APTT inhibits
corrosion of NAB alloy fairly well. The efficiency of inhibition increases with
increasing concentration of APTT, and adsorption of the inhibitor obeys the
Langmuir adsorption isotherm model. Negative values of adsorption free energy
indicate chemical adsorption is spontaneous. The theoretical study showed that
sulfur and nitrogen atoms (S, N7 and N8) were the reactive sites.

Monel is an enigma. Poorly understood and grossly under-researched, the alloy has largely been ignored despite its importance in the first half of the twentieth century in the history of metallurgy and the moderne style. In exterior environments Monel’s weathered appearance is commonly misidentified as Bronze, while in interior contexts, it is regularly assumed as nickel silver. The break-up of the International Nickel Company has scattered historical and technical data, leading to an information vacuum that sees historic Monel painted, waxed, or lacquered, with no grasp of the potential impact on it. The first part of this published work covers the production and processes of the International Nickel Company, the dominance of the Creighton mine, the methods for ore separation and smelting in Ontario, Canada, and the subsequent refining in West Virginia, United States. Covering the impact of both world wars, demand and discoloration, it explains the background on this rare and underappreciated architectural “white metal.”