Technology & Engineering
Corrosion Protection
Corrosion protection refers to the methods and materials used to prevent or slow down the degradation of metal surfaces due to chemical or electrochemical reactions with their environment. This can include the application of protective coatings, such as paints or corrosion-resistant metals, as well as the use of inhibitors or cathodic protection systems to mitigate the effects of corrosion.
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eBook - PDF- Yongchang Huang, Jianqi Zhang, Yongchang Huang, Jianqi Zhang(Authors)
- 2018(Publication Date)
- De Gruyter(Publisher)
Yongchang Huang 11 Protection technology of material corrosion 11.1 Introduction The cause of material corrosion and the different corrosion mechanisms, as well as a variety of factors affecting corrosion, have been discussed in detail in the previ- ous chapters. In short, material corrosion cannot be separated from its surrounding medium, in which the material constitutes a corrosion system. Therefore, to prevent material corrosion, the two factors of material and environment must be taken into account. The methods and measures that are taken to achieve the purpose of preven- ting the corrosion of a material are known as the protection technology of material corrosion. All protection technologies are taken by a two-pronged approach of (1) Changing material composition using the technology of surface treatment and the engineering structural design; and (2) Changing the environment, including processing the medium such as drying, degassing, desalting, etc., and using the corrosion inhibitors and the coating that can isolate environmental. This chapter will introduce several methods that are used frequently in practice to control material corrosion. The classifications are as follows: (1) Selecting correctly corrosion-resistant materials and designing rationally the engineering structures; (2) Using protective coatings; (3) Using electrochemical protection; and (4) Adding corrosion inhibitors. Each protection technology has its application range and condition. For a specific corrosion system, which kind of method is taken and whether to take one method or several methods at the same time majorly depend on several aspects, including the protective effect, the difficulty of construction, and the maintenance efficiency. 11.2 Corrosion preventive design It is well known that a material can finally complete its mission only by being pro- cessed into parts and then assembled into a product or project structure.
eBook - PDF- Dieter Landolt(Author)
- 2007(Publication Date)
- EPFL Press(Publisher)
CHAPTER 12 PROTECTION OF ENGINEERING SYSTEMS AGAINST CORROSION 12.1 PREVENTIVE MEASURES 12.1.1 Introduction The fight against corrosion must begin in the planning stage of a project. In other words, it is necessary to take corrosion into account from the very beginning of a project and during every stage to its completion. The goal is to guarantee a predetermined lifetime for an installation, machine or device at minimum cost, taking into account both the investment and the maintenance costs. Furthermore, the chosen solution must be compatible with environmental regulations, permitting the recycling or elimination of the different components at the end of their use. In many applications (aerospace, nuclear reactors, chemical plants, etc.), safety of operation outweighs all other considerations. A number of different approaches and methods can be used to minimize the corrosion of engineering structures: • appropriate design; • judicious choice of materials; • protective coatings; • corrosion inhibitors; • electrochemical protection. The first two are preventive measures. Taken at the right time, they allow engineers to minimize corrosion problems at marginal additional cost. Protective measures such as the use of coatings, of inhibitors or of electrochemical protection usually require more specific knowledge and often need the intervention of a specialist. They usually generate costs related to maintenance and control. The distinction between preventive and protective measures is not sharp, however; depending on the application, the use of protective coatings can be thought of as a preventive or a protective measure. The concept of corrosion system is of particular importance for the selection of methods of corrosion prevention and protection. Indeed, the corrosion behavior of a metal is influenced by a multitude of electrochemical, mechanical and physical
eBook - ePubCathodic Protection
Industrial Solutions for Protecting Against Corrosion
- Volkan Cicek(Author)
- 2013(Publication Date)
- Wiley-Scrivener(Publisher)
Chapter 6Corrosion Prevention and Protection
In general, corrosion prevention methods’ focus is the interface of the metal surface and solution, since that is where the corrosion mostly takes place. Appropriate metal selection, along with appropriate design, prevents most of the corrosion at metal/solution interface. If metal/solution interaction could be cut completely, corrosion could be completely taken under control. Major corrosion prevention methods are appropriate design, selection of the right material and modification of the composition of the alloy, modification of the environment into a non-corrosive one, use of inhibitors, use of metallic, organic or inorganic coatings, anodic and cathodic protection, etc.Corrosion protective measures are specific to the nature of the material, its environment, and service conditions. Stainless steels that are perfected via lowering the carbon content are used in medical equipment, food processing, and chemical industries exposed to atmospheric and marine conditions. For example, stainless steels that are perfected via lowering the carbon content are used in many areas such as in medical equipments and largely in food processing and chemical industries; therefore, the coatings that are used to coat the stainless steels and other similar materials are exposed to various atmospheric and marine conditions. Among these coatings, metallic coatings are more suitable for acidic, atmospheric, and partially aqueous systems, while paints are preferred more in atmospheric conditions and aqueous solutions. Coatings such as epoxy, polyurethane, and chlorine-rubber polymeric paints can last 15 to 20 years even in extremely corrosive environments. Preparation of metal surface is the first step in the protective coating process. In this step, the metal surface should be properly cleaned by degreasing and desealing. Degreasing is carried out by exposure to trichloroethylene or other volatile organic solvents. Desealing is carried out by sand blasting technique or by acid leaching technique or by other chemical methods. Inhibitors are especially used if replacing the metal is not feasible, such as in closed cooling water systems. Anodic protection is based on passivation of a metal that can be passivated via polarizing the metal in the anodic direction, reducing the corrosion rate down to one in one thousand. Anodic protection is mostly implemented in water and acidic environments, such as in sulfuric acid tanks. Cathodic protection appears to be the most effective and economic method to prevent corrosion in general in underground, water, and underwater systems, and in specific in high-pressure natural gas and oil pipeline systems, pier bases, ships, water and petroleum storage tanks, containers carrying chemicals, heat exchangers, reinforced concrete steels, etc. In this chapter, several practical methods to prevent corrosion will be reviewed.
eBook - ePubCorrosion Control for Offshore Structures
Cathodic Protection and High-Efficiency Coating
- Ramesh Singh(Author)
- 2014(Publication Date)
- Gulf Professional Publishing(Publisher)
Section 1 Basics Concept of Corrosion
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Chapter OneNeed for the Study of Corrosion
Abstract
For many developed nations, corrosion can cause structural damages with costs approaching 3.5 to 4.5% of the gross national product. This financial burden represents the quantifiable losses associated with corrosion, but losses that are not quantifiable are also part of the cost to industry and society. The study of corrosion can help industry recognize and prevent such losses. This chapter explains the basic need for the study of corrosion, before introducing the subject of corrosion prevention. Cathodic protection and the application of coatings are two methods of corrosion prevention to be discussed.Keywords Corrosion Environmental damages Loss of production Economics and cost of corrosion Product contamination Capital costIntroduction
From the perspective of environment, the corrosion activity is a natural phenomenon that is necessary for sustaining the natural balance. Corrosion is a great leveler of engineering materials in that it tries to revert the metal back to its most stable form. However, from an engineer’s perspective, corrosion could be seen as a destructive attack of nature on metal. This destruction of metal is, however, brought about by nature’s chemical or electrochemical reaction. It causes significant loss of material which leads to losses in terms of productivity and cost of maintenance, repair and replacements, and restoration. This does not included damage to property and the occasional loss of lives and injuries associated with failures resulting from corrosion.Corrosion occurs in every aspect of modern life; every life is affected, though not everyone is aware of the corrosion happening around them. It is an all pervasive and 24/7 activity.The impact of corrosion is three directional, the three aspects being economic, safety, and environment. The impact of corrosion, and the prevention thereof, is felt economically, and affects the safety and environmental conservation of resources. In the succeeding discussions we will see how these three aspects manifest themselves.
- Monzer Fanun(Author)
- 2014(Publication Date)
- Elsevier(Publisher)
Chapter 20The Role of Corrosion Inhibitors in Protecting Metallic Structures against Corrosion in Harsh Environments
El-Sayed M. SherifCenter of Excellence for Research in Engineering Materials (CEREM), College of Engineering, King Saud University, Al-Riyadh, Saudi Arabia Electrochemistry and Corrosion Laboratory, Department of Physical Chemistry, National Research Centre (NRC), Cairo, EgyptAbstract
The present review discusses the latest reported studies on the role of corrosion inhibitors in mitigating the corrosion of metals and alloys in corrosive aqueous media and in the atmosphere. Included is basic information about inhibitors such as their definitions, classifications, efficiencies, and applications in the industrial sector as well as the most frequently used techniques, either conventional or nonconventional, to evaluate their efficiencies in controlling corrosion. Corrosion inhibitors are usually chemical compounds used in low concentrations to mitigate the corrosion rate of metallic materials when they are in contact with aggressive media. The use of corrosion inhibitors in this regard has been one of the most successful methods in minimizing corrosion in aqueous solutions and in the atmosphere. Compounds with this feature are classified as passivating, cathodic, organic, precipitation, and volatile corrosion inhibitors. Each class of these inhibitors is divided into subcategories that reflect their mechanism in controlling the corrosion rate either by decreasing the severity of the surrounding environment or by modifying or blocking the surface of the material to be protected. This review also reports the evaluation of the inhibition efficiency of corrosion inhibitors by using both conventional and modern measuring techniques. Conventional methods include the use of gravimetric weight-loss, electrochemical anodic, linear, cathodic, and cyclic polarization, and chronoamperometric current-time techniques. The nonconventional tests involve employing the electrochemical impedance spectroscopy and electrochemical quartz crystal microbalance. The characterization of the surface of the materials after being inhibited is usually performed by scanning electron microscopy, infrared spectroscopy, UV-visible spectroscopy, energy dispersive X-ray analyzer, and so on. Also covered in this chapter is the use of corrosion inhibitors in industry.
eBook - PDF- Sparrow Consulting(Author)
- 2021(Publication Date)
- Future Managers(Publisher)
MODULE 2 Metal protection By the end of this module, you should be able to: • describe corrosion as the destruction of material as a result of chemical, electrochemical or metallurgical reaction between the material and the environment; • explain the two main classes of corrosion; • explain the following forms of corrosion: – surface corrosion – stress corrosion – galvanic corrosion – intercrystalline corrosion – pitting corrosion; • explain the most common types of corrosion tests; • describe what each of the following metal protection processes involves: – cathodic protection – electroplating – anodising – phosphating; • describe the following processes used to prepare steel for spray painting: – sandblast cleaning – descaling – grease removal; • explain the following painting processes: – air spray painting – airless spray painting – electrostatic spray painting – dip painting; and • list the advantages and disadvantages of using each of the painting processes. Introduction Metal is a solid material that is usually hard, shiny and a good conductor of heat and electricity. Metals can be pressed or moulded into different shapes without breaking. They are directly or indirectly used in most of the things that surround us. For example, a cell phone has many different types of metals inside and outside of it, which are needed to make it work. Unfortunately, metals’ major weakness is corrosion, which is 24 Module 2 • Metal protection one of the main reasons why most metal-based structures fail. In this section, you will learn more about the following: • Corrosion and the different types of corrosion • Causes of corrosion and how to test for corrosion • How to protect metals against corrosion • How to prepare a surface for the different types of painting.
- Einar Mattsson(Author)
- 2023(Publication Date)
- CRC Press(Publisher)
6 Corrosion Protection One can combat corrosion in many different ways, e.g.:- by controlling the electrode potential so that the metal becomes immune or passive, i.e. by applying cathodic or anodic protection,
- by reducing the rate of corrosion with the aid of corrosion inhibitors added to the environment, or
- by applying an organic or inorganic protective coating.
6.1 Cathodic Protection
The corrosion rate of a metal surface in contact with an electrolyte solution is strongly dependent on the electrode potential. In most cases the corrosion rate can be reduced considerably by shifting the electrode potential to a lower value. This can usually be brought about by loading the surface of the object to be protected with a cathodic current, so that a negative polarisation is produced. This type of protection is therefore called cathodic protection. If the electrode potential is shifted so far that it corresponds to a point in the immunity domain of the potential-pH diagram the metal will be thermodynamically stable and corrosion cannot take place (Fig. 72 ). One can then refer to complete cathodic protection. If the shift in potential is less, the protection is said to be incomplete, but can nevertheless be of great practical value. For economic reasons, cathodic protection is often restricted to such parts of the structure, where the risk of corrosion is of particular importance, i.e. to so-called “hot spots”.6.1.1 Cathodic protection with impressed current
When the cathodic current to the surface of the object to be protected is supplied with the aid of an external current source (e.g. a transformer-rectifier unit) and an auxiliary anode (Fig. 73 ) then the protection is said to be of the electrolytic type.In this case either soluble or inert anodes can be used. Soluble anodes can be made of steel (scrapped steel girders, rails etc.). The usual materials for the inert anodes are magnetite, silicon iron, graphite, lead or platinised titanium/niobium. For the protection of steel reinforcements in concrete there are flexible anodes of conductive plastics, consisting of a copper wire core surrounded by an electrically-conducting plastics covering. The potential of the structure to be protected can be held at the desired value with the aid of a potentiostat and a permanent reference electrode which controls the flow of current from the rectifier. This technique is applied primarily when there are variations in the protective current demand. Cathodic protection with impressed current is used, for example, in the following cases:
eBook - ePub- Volkan Cicek(Author)
- 2014(Publication Date)
- Wiley-Scrivener(Publisher)
To reduce the already low current used in anodic protection even further a current-cutter is used; thus, the current consumed can be reduced down to 1%, e.g., current can be applied for 6 seconds and not for the following 600 seconds. The current provided for 6 seconds is sufficient to anodically passivate the regions that corrode within the 600 seconds; therefore, many pieces of equipment can be anodically protected using the same transformer-rectifier unit.7.5.2 Cathodic Protection
One of the most effective means of corrosion prevention is cathodic protection that can be used for all types of corrosion and may, in some situations, completely stop corrosion. Cathodic protection protects the metallic structure by converting it from anode to cathode externally, providing the electrons needed for cathodic reactions. Cathodic protection techniques are widely implemented in the industry for metallic structures such as underground pipelines, ports, piers, ships, petroleum storage tanks, water storage tanks, etc. that are embedded in electrolytes such as water, soil, concrete, etc.Cathodic protection was first tried on a military ship named ‘Samarang’ by Sir Humpry Davy in 1824. The ship’s body that was made of copper was protected using zinc anodes; however, as a result of a successful corrosion inhibition, copper ions have been removed from the system, which led to living organisms such as moss covering the ship’s body, which in turn gave the impression that the cathodic protection attempt was unsuccessful. Cathodic protection was also used as early as 1836, by dipping iron sheets into molten zinc to protect war ships from corrosion. After about a century, cathodic protection was used again, this time for the protection of underground pipelines, and in the 1950s, it began to be commonly used for water and oil storage tanks, ships, dams, pier bases, reinforced concrete steel bars, etc.Cathodic protection simply involves supplying, from an external source, electrons to the metal to be protected, making it a cathode. Normally, electrons are produced at the anode and flow to the cathode, where they are used at the cathodic reaction. If these electrons are provided externally, then the anodic reaction cannot produce any more electrons, while the cathodic reaction rate increases, and the anodic reactions do not take place at the surface of the metal to be protected, but on the surface of another anode in the cathodic protection system.
- Paul Angus, Carl Harrop, Steve Ingle, David Considine, Danny Davis, David Greenall, Allan Homewood, Lynne Jack, Brian Johnston, Derek King, John Turner(Authors)
- 2014(Publication Date)
Open systems such as domestic water services, which are intended to convey aerated water, will therefore need a different approach to corrosion control 12.1.2 Definition Corrosion may be defined as the reaction of a metal with its environment resulting in damage which impairs the function of a component or system. Non-metallic materials can also break down and this is generally termed degradation. Corrosion or degradation may be also exacerbated by the presence of mechanical forces, e.g. stress or fatigue, which are created by the service conditions, and are often very difficult to predict. The following sections cover the factors which affect corrosion, how to assess the local environment and methods of prevention. Water treatment, which may be used to control corrosion and scaling is covered elsewhere. 12.1.3 Metallic and non-metallic materials 12.1.3.1 Metals Corrosion is the principal cause of premature failure in metallic building services components and systems. Not only is it responsible for increased maintenance but also losses in efficiency, particularly in heating and air conditioning systems. 12 Corrosion and Corrosion Protection Summary Corrosion is a complex issue and one that can cause significant damage and performance loss to plumbing systems where not ‘designed-out’ or controlled. This chapter aims to provide the basic information to inform the designer in the material selection and system design in order to minimise the potential for corrosion. 12.1 Introduction 12.2 Factors affecting corrosion 12.3 Assessment of corrosive environments 12.4 Prevention of corrosion 12.5 Chemical cleaning and passivation References This publication is supplied by CIBSE for the sole use of the person making the download. The content remains the copyright property of CIBSE
eBook - PDFCorrosion Prevention and Protection
Practical Solutions
- Edward Ghali, V. S. Sastri, M. Elboujdaini(Authors)
- 2007(Publication Date)
- Wiley(Publisher)
39. S. Srinivasan, R.D. Kane, Materials and Corrosion Resources on the Internet, 2nd NACE Latin American Corrosion Congress , Rio de Janeiro, Brazil, September 1996. 328 Corrosion Prevention and Protection Part II 6 The Forms of Corrosion Note : Some reference citations in this chapter refer to Handbooks containing several individual references. These are indicated in the text as (ASTM G 52004) 4 , for example, and the addition of RO4 in the reference list stands for revised 2004. 6.1 Corrosion Reactions Corrosion of materials is a direct chemical reaction of a metal with its environment or a flow of electricity in an electrochemical reaction in an aggressive medium such as natural media (atmospheric, water or underground) or process media. Local cells (short-circuited) electrochemical cells of the same active metal or between an active metallic surface and that of another more noble conducting material can give rise to corrosion. The following general reaction may be written as: a A þ b B ! c C þ d D where a moles of solid substance A (metal for example react with b moles of substance B (environment) to form c moles of substance C (oxidized metal or material) and d moles of D (reduced environment). A ‘wet’ reaction of iron in an oxygenated aqueous medium can be represented by the equation: Fe þ 0 : 5 H 2 O þ 0 : 75 O 2 ! 0 : 5 Fe 2 O 3 H 2 O A ‘dry’ reaction of corrosion of iron can be written as: Fe þ 0 : 75 O 2 ! 0 : 5 Fe 2 O 3 Oxidation of metals includes all reactions in which the charge is transported through a film of reaction product on the metal surface. Parabolic, logarithmic, asymptotic, rates involve the presence of a rate-determining film, while linear growth rates correspond to the absence of such films. These reactions are generally considered as dry reactions. Corrosion Prevention and Protection: Practical Solutions V. S. Sastri, E. Ghali and M. Elboujdaini # 2007 John Wiley & Sons, Ltd
eBook - PDF- DENNIS A SNOW(Author)
- 2013(Publication Date)
- Newnes(Publisher)
30 Corrosion MICorrT Cortest Laboratories Ltd BSc, MSc, PhD, Contents 30.1 Corrosion basics 30/3 30.1.1 Definitions of corrosion 30/3 30.1.2 Electrochemical corrosion 30/3 30.1.3 Cracking mechanisms 30/7 30.1.4 Non-electrochemical corrosion 30/9 30.2 The implications of corrosion 30/9 30.2.1 Economics 30/9 30.2.2 Safety 30/10 30.2.3 Contamination of product 30/10 30.3 Materials selection 30/10 30.3.1 Sources of information 30/10 30.3.2 Aqueous systems 30/10 30.3.3 Non-aqueous processes 30/12 30.3.4 High-temperature environments 30/12 30.3.5 Influence of process variables on material selection 30/13 30.3.6 Influence of external environment 30/15 30.4 Design and corrosion 30/17 30.4.1 Shape 30/17 30.4.2 Stress 30/17 30.4.3 Fabricational techniques 30/18 30.4.4 Design for inspection 30/18 30.5 Uses and limitations of constructional materials 30/19 30.5.1 Steels and cast irons 30/19 30.5.2 Stainless steels 30/19 30.5.3 Nickel alloys 30/20 30.5.4 Copper alloys 30/20 30.5.5 Miscellaneous metallic materials 30/20 30.5.6 Linings and coatings 30/21 30.6 Specifying materials 30/21 30.6.1 Compositional aspects 30/21 30.6.2 Mechanical properties 30/22 30.6.3 Certification 30/22 30.7 Corrosion-control techniques 30/22 30.7.1 Painting 30/22 30.7.2 Cathodic protection 30/23 30.7.3 Anodic protection 30/24 30.7.4 Corrosion inhibitors 30/24 30.8 Corrosion monitoring 30/24 30.8.1 Physical examination 30/25 30.8.2 Exposure coupons and electrical resistance probes 30/25 30.8.3 Electrochemical corrosion monitoring 30/25 30.8.4 Thin-layer activation 30/26 30/1 Michael J Schofield This page intentionally left blank Corrosion basics 30/3 30.1 Corrosion basics 30.1.1 Definitions of corrosion Corrosion is generally taken to be the waste of a metal by the action of corrosive agents. However, a wider definition is the degradation of a material through contact with its environment.
eBook - PDF- H Böhni(Author)
- 2005(Publication Date)
- Woodhead Publishing(Publisher)
8 Electrochemical techniques for Corrosion Protection and maintenance R B POLDER TNO Building and Construction Research, The Netherlands 8.1 Introduction Corrosion Protection of steel reinforcement in concrete can be lost due to ingress of chloride ions or carbonation of concrete. Conventional methods for concrete repair aim at removing all chloride-contaminated or carbon-ated concrete, cleaning the steel and reprofiling the surface with new, chloride-free and alkaline, cementitious concrete or mortar. In general, this is a cumbersome procedure that involves heavy labour and produces large amounts of noise, dust and waste material. Unless all chloride is removed, in particular from the steel surface including the inside of corrosion pits, corrosion may re-initiate after a short time. Consequently, conventional repairs can be expensive and may not be durable. During the last decades, electrochemical maintenance methods have been introduced which overcome these disadvantages of conventional repair (COST 521, 2003). 8.2 Types of electrochemical techniques available One possible electrochemical method is cathodic protection (CP), which requires a permanently installed electrode material on or in the structure and a permanent current flow of low density (Pedeferri, 1992, 1998; Page, 1997; Polder, 1998a,b). CP reduces the corrosion rate by depressing the steel potential, which neutralises the corrosive effect of chloride ions or carbon-ation. Consequently, chloride-containing and carbonated concrete can be left in place. Application of current in cases where corrosion has not yet started is termed Cathodic Prevention (CPre), which will be discussed alongside CP. Another method is electrochemical chloride removal (ECR) that is also called electrochemical chloride extraction (ECE) or desalination, which removes chloride from contaminated concrete by passing a direct current of a relatively high density for a limited period of time (Mietz, 1998). The 215
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