LUBRICATING OIL AGAINST CORROSION BASIC INFORMATION

Lubricants are not generally regarded as being corrosive, and in order to appreciate how corrosion can occur in lubricant systems it is necessary to understand something of the nature of lubricants. Once, lubricants were almost exclusively animal or vegetable oils or fats, but modern requirements in the way of volume and special properties have made petroleum the main source of supply. In volume, lubricants now represent about 2% of all petroleum products; in value, considerably more.

There are many hundreds of different varieties of lubricants, many of them tailored to meet particular requirements. Lubricating greases are solid or semi-solid lubricants made by thickening lubricating oils with soaps, clays, silica gel or other thickening agents. Synthetic lubricants, which will operate over a very wide range of temperature, have been developed mainly for aviation gas-turbine engines.

These are generally carboxylic esters and are very expensive products. The main function of most lubricants is to reduce friction and wear between moving surfaces and to abstract heat. They also have to remove debris from the contact area, e.g. combustion products in an engine cylinder, swarf in metal-cutting operations.


Mineral lubricants may be distillates or residues derived from the vacuum distillation of a primary distillate with a boiling point range above that of gas oi1’*2*T3.h ey are mixtures of hydrocarbons containing more than about 20 carbon atoms per molecule, and range from thin, easily flowing ‘spindle’ oils to thick ‘cylinder’oils.

For hydrocarbons having the same number of carbon atoms per molecule, the higher the proportion of carbon to hydrogen, the more viscous the oil and the lower the viscosity index.


Distillate lubricating oils can be conveniently divided into three groups -low viscosity index oils (LVI oils), medium viscosity index oils (MVI oils) and high viscosity index oils (HVI oils). LVI oils are made from naphthenic distillates, with low wax contents so that costly dewaxing is not required.

MVI oils are produced from both naphthenic and paraffinic distillates; the paraffinic distillates have to be dewaxed. HVI oils are prepared by the solvent extraction and dewaxing of paraffnic distillates. Solvent extraction is a physical process which removes the undesirable constituents, thereby improving viscosity index and the oxidation and colour stability.

White oils are obtained by the more drastic refining of low viscosity lubricating oil distillates to remove unsaturated compounds and constituents that impart colour, odour and taste. They are usually solvent extracted and then repeatedly treated with strong sulphuric acid or oleum and alkali, and finally ‘clay’-treated to remove surface-active compounds.

Acid and clay treating is expensive and is being superseded by hydrofinishing, a catalytic hydrogenation
treatment. The residues from the vacuum distillation can also be refined to provide very viscous lubricants. The residues from paraffinic base oils are generally solvent extracted and dewaxed. The main use of these products (bright stocks) is as blending components for heavy lubricants.

Thus residues from naphthenic base oils, which are also used as blending components for heavy lubricants, are normally not extracted. The performance characteristics of a lubricating oil depend on its origin and on the refining processes employed, and in order to ensure consistent properties these are varied as little as possible. Some aero-engine builders insist on a complete re-evaluation of a lubricant, costing many thousands of pounds, whenever there is a change of source (crude) or refining process.

CORROSION OF IRON AND STEEL AND PREVENTION BASIC INFORMATION AND TUTORIALS

What causes corrosion on Iron and Steel?

Principles of Corrosion.

Corrosion may take place by direct chemical attack or by electrochemical (galvanic) attack; the latter is by far the most common mechanism. When two dissimilar metals that are in electrical contact are connected by an electrolyte, an electromotive potential is developed, and a current flows.

The magnitude of the current depends on the conductivity of the electrolyte, the presence of high resistance “passivating” films on the electrode surfaces, the relative areas of electrodes, and the strength of the potential difference. The metal that serves as the anode undergoes oxidation and goes into solution (corrodes).

When different metals are ranked according to their tendency to go into solution, the galvanic series, or electromotive series, is obtained. Metals at the bottom will corrode when in contact with those at the top; the greater the separation, the greater the attack is likely to be.

Table 4-14 is such a ranking, based on tests by the International Nickel Company, in which the electrolyte was seawater.

The nature of the electrolyte may affect the order to some extent. It also should be recognized that very subtle differences in the nature of the metal may result in the formation of anode-cathode galvanic cells: slight differences in composition of the electrolyte at different locations on the metal surface, minor segregation of impurities in the metal, variations in the degree of cold deformation undergone by the metal, etc.

It is possible for anode-cathode couples to exist very close to each other on a metal surface. The electrolyte is a solution of ions; a film of condensed moisture will serve.

Corrosion Prevention.

An understanding of the mechanism of corrosion suggests possible ways of minimizing corrosion effects. Some of these include:

(1) avoidance of metal combinations that are not compatible,

(2) electrical insulation between dissimilar metals that have to be used together,

(3) use of a sacrificial anode placed in contact with a structure to be protected (this is an expensive technique but can be justified in order to protect such structures as buried pipelines and ship hulls),

(4) use of an impressed emf from an external power source to buck out the corrosion current (called cathodic protection),

(5) avoiding the presence of an electrolyte—especially those with high conductivities, and

(6) application of a protective coating to either the anode or the cathode.  

CEMENT PASTE CORROSION PREVENTION BASIC AND TUTORIALS

CEMENT PASTE CORROSION PREVENTION BASIC INFORMATION
How To Prevent Corrosion Of Cement Paste?


The corrosion of cement paste occurs because chemical reaction can happen between its external environment and internal environment. The corrosive compound must be the solution with a certain concentration, such as high temperature, proper humidity, fast flow, and the corrosion of steel bar.

Thus, the following measures can be adopted in the use of cement:

1) Select the cement varieties reasonably based on the features of the erosive environment. For example, the cement whose hydrates contains a little calcium hydroxide has high capacity to resist erosive effects of soft water and others; the anti-sulfate cement whose content of tri-calcium aluminate is less than 5% can resist the sulfate erosion.

2) Raise the Density of Cement Paste. The amount of mixing water for Portland cement should be strictly controlled in order to reduce the pore space.

The water theoretically needed in hydration of Portland cement is only 23% but much more mixing water (accounting for about 40%-70% of the cement mass) is needed in practical projects, and the pores connect to each other after the excessive water evaporates, so the erosive media go through the inner part of cement easily to accelerate the corrosion of cement.

The mix proportion should be designed reasonably in order to improve the compactness of cement concrete. Low water-cement ratio and the best construction method should be adopted as much as possible.

In addition, the insoluble calcium carbonate shell or calcium fluoride and thin silica gel film generated by conducting carbonization or fluosilicic acid treatment on the surface of concrete and mortar can increase the compactness of the surface and decrease the infiltration of erosive media.

3) Add a Protective Layer. The resistant stone, ceramic, plastic, and waterproof material are covered on the surface of cement paste, forming a impermeable layer for protection, to prevent the corrosion media contacting with cement paste directly.

STEEL REINFORCED CONCRETE STRUCTURES ASSESSMENT AND REPAIR OF CORROSION FREE EBOOK DOWNLOAD LINKE

STEEL REINFORCED CONCRETE STRUCTURES ASSESSMENT AND REPAIR OF CORROSION FREE EBOOK
Free E-Book Download Link Of Steel-Reinforced Concrete Structures: Assessment and Repair of Corrosion

A Practical Guide to Maintenance
Carrying a billion-dollar price tag, corrosion of reinforced concrete is the enemy of every country’s investment in real estate. The widespread and long-term use of reinforced concrete makes its correct and proper examination, maintenance, and repair paramount.

Steel-Reinforced Concrete Structures: Assessment and Repair of Corrosion explains the corrosion of reinforced concrete from a practical point of view, highlighting protective design and repair procedures.

The book begins with a discussion of the corrosion phenomena, the effect of concrete properties on corrosion, and the precautions available in the construction stage to mitigate corrosion. It covers the theoretical and practical methods in evaluating the concrete structures and new, practical methods to protect steel reinforcement.

The book also includes methods established in the last decade that provide new ways of protecting steel-reinforced bars and the traditional and advanced repairing methods. The author explains the importance of implementing an integrity management system to provide a comprehensive maintenance strategy and concludes with coverage of the traditional, time-tested, and advanced repair techniques.

A special feature is a chapter focusing on the advance maintenance plan philosophy and risk-based maintenance for reinforced concrete structures.

The author examines economic analysis procedures and the probability of structural failures to define structure risk assessment. He covers precautions and recommendations for protecting the reinforced concrete structures from corrosion based on codes and specifications. He uses case histories from all over the world to demonstrate the widespread application and range of advanced repair techniques and presents a practical guide to the maintenance of concrete structures. The book provides procedures for corrosion diagnosis and determining the appropriate methods for repair, as well as economic models for on-site decision making.

The Author
Mohamed A. El-Reedy's background in structural engineering. His main area of researches is reliability of concrete and steel structure. He has provided consulting to different engineering companies and oil and gas industries in Egypt and to international companies as the International Egyptian Oil Company (IEOC) and British Petroleum (BP). Moreover, he provides different concrete and steel structure design package for residential buildings, warehouses and telecommunication towers and electrical projects with WorleyParsons Egypt. He has participated in Liquified Natural Gas (LNG) and Natural Gas Liquid (NGL) projects with international engineering firms. Curently, Dr. El-Reedy is responsible for reliability, Inspection and maintenance strategy for onshore concrete structures and offshore steel structure platforms. He has performed these tasks for hundred structures in Gulf of Suez in the red sea.

Dr. El-Reedy has consulted with and trained executives at many organizations, including the Arabian American Oil Compnay (ARAMCO), bp, Apachi, Abu Dhabi Marine Operating Company (ADMA), the Abu Dhabi National Oil Company and King Saudi's Interior ministry, Qatar Telecom, EGPC , (SAPIC) , the Kuwait Petroleum Corporation, and Qatar petrochemical Company (QAPCO). He has taught technical courses about repair and maintenance for reinforced concrete structures and the advanced materials in concrete industry worldwide , especially in the Middle East, malaysia and singapore.

Dr. El-Reedy has written numerous publications and presented many papers at local and international conferences sponsored by the ASCE, CSCE, ACI, API and in technical committe for OMAE conference sponsor by ASME.He has published many research papers in international technical journals and has authored four books about total quality management, quality management and quality assurance, economic management for engineering projects, and repair and protection of reinforced concrete structures. He received his bachelor's degree from Cairo University in 1990, his master's degree in 1995, and his Ph.D from Cairo University in 2000.

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PREVENTION OF CORROSION OF ALUMINUM BASIC AND TUTORIALS

PREVENTION OF CORROSION OF ALUMINUM BASIC INFORMATION
How To Prevent Aluminum Corrosion?


Although aluminum ranks high in the electromotive series of the metals, it is highly corrosion resistant because of the tough, transparent, tenacious film of aluminum oxide that rapidly forms on any exposed surface.

It is this corrosion resistance that recommends aluminum for building applications. For most exposures, including industrial and seacoast atmospheres, the alloys normally recommended are adequate, particularly if used in usual thicknesses and if mild pitting is not objectionable.

Pure aluminum is the most corrosion resistant of all and is used alone or as cladding on strong-alloy cores where maximum resistance is wanted. Of the alloys, those containing magnesium, manganese, chromium, or magnesium and silicon in the form of MgSi2 are highly resistant to corrosion.

The alloys containing substantial proportions of copper are more susceptible to corrosion, depending markedly on the heat treatment.

Certain precautions should be taken in building. Aluminum is subject to attack by alkalies, and it should therefore be protected from contact with wet concrete, mortar, and plaster.

Clear methacrylate lacquers or strippable plastic coatings are recommended for interiors and methacrylate lacquer for exterior protection during construction. Strong alkaline and acid cleaners should be avoided and muriatic acid should not be used on masonry surfaces adjacent to aluminum.

If aluminum must be contiguous to concrete and mortar outdoors, or where it will be wet, it should be insulated from direct contact by asphalts, bitumens, felts, or other means. As is true of other metals, atmospheric-deposited dirt must be removed to maintain good appearance.

Electrolytic action between aluminum and less active metals should be avoided, because the aluminum then becomes anodic. If aluminum must be in touch with other metals, the faying surfaces should be insulated by painting with asphaltic or similar paints, or by gasketing. Steel rivets and bolts, for example, should be insulated.

Drainage from copper-alloy surfaces onto aluminum must be avoided. Frequently, steel surfaces can be galvanized or cadmium-coated where contact is expected with aluminum. The zinc or cadmium coating is anodic to the aluminum and helps to protect it.

CORROSION RESISTANCE METHODS FOR STRUCTURAL STEEL BASIC AND TUTORIALS

CORROSION RESISTANCE METHODS FOR STRUCTURAL STEEL BASIC INFORMATION
What Are The Corrosion Resistance Methods For Structural Steel?

Since steel contains three of the four elements needed for corrosion, protective coatings can be used to isolate the steel from moisture, the fourth element. There are three mechanisms by which coatings provide corrosion protection (Hare, 1987):

1. Barrier coatings work solely by isolating the steel from the moisture. These coatings have low water and oxygen permeability.

2. Inhabitive primer coatings contain passivating pigments. They are low-solubility pigments that migrate to the steel surface when moisture passes through the film to passivate the steel surface.

3. Sacrificial primers (cathodic protection) contain pigments such as elemental zinc. Since zinc is higher than iron in the galvanic series, when corrosion conditions exist the zinc gives up electrons to the steel, becomes the anode, and corrodes to protect the steel.

There should be close contact between the steel and the sacrificial primer in order to have an effective corrosion protection.

Cathodic protection can take forms other than coating. For example, steel structures such as water heaters, underground tanks and pipes, and marine equipment can be electrically connected to another metal that is more reactive in the particular environment, such as magnesium or zinc.

Such reactive metal (sacrificial anode) experiences oxidation and gives up electrons to the steel, protecting the steel from corrosion. Figure 3.32 illustrates an underground steel tank that is electrically connected to a magnesium sacrificial anode (Fontana and Green, 1978).

Above is a diagram on Cathodic protection of an underground pipeline using a magnesium sacrificial anode.

STEEL CORROSION BASICS AND TUTORIALS

STEEL CORROSION BASIC INFORMATION
What Makes The Steel Corrode? What Is Steel Corrosion?


Corrosion is defined as the destruction of a material by electrochemical reaction to the environment. For simplicity, corrosion of steel can be defined as the destruction that can be detected by rust formation.

Corrosion of steel structures can cause serious problems and embarrassing and/or dangerous failures. For example, corrosion of steel bridges, if left unchecked, may result in lowering weight limits, costly steel replacement, or collapse of the structure.

Other examples include corrosion of steel pipes, trusses, frames, and other structures. It is estimated that the cost of corrosion of the infrastructure in the United States alone is $22.6 billion each year (corrosion costs web site, 2009).

The infrastructure includes (1) highway bridges, (2) gas and liquid transmission pipelines, (3) waterways and ports, (4) hazardous materials storage, (5) airports, and (6) railroads.

Corrosion is an electrochemical process; that is, it is a chemical reaction in which there is transfer of electrons from one chemical species to another. In the case of steel, the transfer is between iron and oxygen, a process called oxidation reduction.

Corrosion requires the following four elements (without any of them corrosion will not occur):
1. an anode—the electrode where corrosion occurs
2. a cathode—the other electrode needed to form a corrosion cell
3. a conductor—a metallic pathway for electrons to flow
4. an electrolyte—a liquid that can support the flow of electrons


Steel, being a heterogeneous material, contains anodes and cathodes. Steel is also an electrical conductor. Therefore, steel contains three of the four elements needed for corrosion, while moisture is usually the fourth element (electrolyte).

The actual electrochemical reactions that occur when steel corrodes are very complex. However, the basic reactions for atmospherically exposed steel in a chemically neutral environment are dissolution of the metal at the anode and reduction of oxygen at the cathode.

Contaminants deposited on the steel surface affect the corrosion reactions and the rate of corrosion. Salt, from deicing or a marine environment, is a common contaminant that accelerates corrosion of steel bridges and reinforcing steel in concrete.

The environment plays an important role in determining corrosion rates. Since an electrolyte is needed in the corrosion reaction, the amount of time the steel stays wet will affect the rate of corrosion.

Also, contaminants in the air, such as oxides or sulfur, accelerate corrosion. Thus, areas with acid rain, coal-burning power plants, and other chemical plants may accelerate corrosion.