control of corrosion on underwater piles ppt free download

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1. CONTROL OF CORROSION OF UNDERWATER PILES Presented by: Avinash Shaw Roll no. 11/CE/45 Department of Civil Engineering NIT Durgapur
2. Introduction Corrosion is the destruction of metals and alloys by the chemical reaction with the environment. Generally many traditional metal parts are used with lighter polymeric components but these are impervious to electrochemical corrosion so even with the proper selection of base metals, there is no absolute way to eliminate corrosion.
3. On steel piling in seawater, the more chemically active surface areas (anodes) are metallically coupled through the piling itself to the less chemically active surface areas (cathodes) resulting flow of electricity and corrosion of anodic areas. Generally corrosion occurs when local anodic and cathodic areas continually shift about randomly but sometimes they do not shift position end, therefore the metal suffers localized attack and pitting occurs. In general smaller the anode area relative to the cathode area, the deeper the pitting
4. Corrosion Caused By The Difference Of The Dissolved Oxygen Concentration
5. SPLASH ZONE ZONES ATMOSPHERIC ZONE SUBMERGED ZONE TIDAL ZONE Depending upon time of wetness, temperature, pollutants etc. Atmospheric corrosion is responsible for a large fraction of the total corrosion in the world. CORROSION RATE(without protection) < 0.1 mm/year
6. SPLASH ZONE ZONES ATMOSPHERIC ZONE SUBMERGED ZONE TIDAL ZONE The splash/spray zone can be characterized by as an aerated sea water environment where exposed material are almost continually wet and biofouling do not attach. CORROSION RATE(without protection) 0.3 mm/year
7. SPLASH ZONE ZONES ATMOSPHERIC ZONE SUBMERGED ZONE TIDAL ZONE The tidal zone is an environment where metals are alternately submerged in seawater and exposed to the splash zone as the tide fluctuates. CORROSION RATE (without protection) 0.1-0.3 mm/year
8. SPLASH ZONE ZONES ATMOSPHERIC ZONE SUBMERGED ZONE TIDAL ZONE The submerged/ shallow ocean environment zone usually characterized by well aerated water combined with marine biofouling organism of both the plant and animal variety. CORROSION RATE(without protection) 0.1-0.2 mm/year
9. Phase 1 of the program is the programmatic assessment or planning stage of the project. For the planning stage, three main requirements sought, budget and schedule needed to overcome the problem raised PHASE 1 PHASE 2 PHASE 3
10. Phase 2 of the program involves physical assessment and actual remediation. Inspections for severity of corrosion are conducted in this phase to determine what strategy or methods are most suitable to be applied. PHASE 1 PHASE 2 PHASE 3
11. Phase 3 of the program mainly deals with future monitoring of the repaired structure. Systematically identifying and managing the existing resources can be done by implementing internal or external monitoring system using current PHASE 1 PHASE 2 PHASE 3
12. PROTECTIVE COATING CATHODIC PROTECTION ANODE DELIVERY SYSTEM Application of FRP composites
13. Protective Coating In order to protect metals from corrosion, the contact between the metal and the corrosive environment is to be cut off. This is done by coating the surface of metals with a continuous non-porous material inert to the corrosive atmosphere. Surface coatings are broadly classified into three Metallic coatings Inorganic Coatings Organic Coatings
14. Protective Coatings 1. Inorganic Zinc Sillicates Primers 2. High Build Epoxy Coatings 3. Aliphatic Polyurethane Topcoats 4. Zinc Rich Epoxy Primers 5. Non-Skid Deck Coatings
15. arrest rust creep, or undercutting of the coatings surrounding the damaged area high degree of resistance to heat and chemical spills Inorganic Zinc Silicates Primers
16. Epoxies are generally more abrasion and chemical resistant than primers These are poor resistance of ultra violet from sunlight and most will chalk and fade rapidly. High Build Epoxy Coating s
17. optimum resistance to UV and high degrees of flexibility and chemical resistance. maintain a very high level of cosmetic gloss and color retention and can be cleaned very easily with low pH detergents and fresh water pressure washing. Aliphatic Polyuret hane Topcoats
18. high level of service and are more tolerant to compromised surface preparation and ambient weather conditions maintaining damaged areas and breakdown of the coatings systems Zinc Rich Epoxy Primers
19. normally incorporate very course aggregates for an exaggerated profile. They are applied in very high film builds and normally without a zinc rich primer. Non-Skid Deck Coatings
20. CATHODIC PROTECTION Cathodic protection is an electrochemical process which halts the corrosion of metals in a particular environment by superimposing an electrochemical cell more powerful than the corrosion cell. Sacrifical Anodes are fitted or bonded to the metal to be protected. The implementation is simple, all you need is an anode, a power supply and engineering talent.
21. These are similar to the cathodic protection method in philosophy. These are designed on the design basis of maximum current distribution for the lowest possible cost, with the most long-term reliability.
22. Anode delivery system Pile Mounted Anode Retractable Anode
23. Sled Anode Suspension Anode
24. Application of FRP composites The poor durability of conventional corrosion repairs has led to increased interest for its replacement by fiber reinforced polymers. Although dry conditions are favorable but availability of resins that can cure in water has made it possible. Saturating FRP with resin and installing is complex but benificial in costly repairs and rapid deterioration.
25. Fibre reinforced polymers have long been used for the repair and retrofit of concrete structural elements. Lightweight, high strength and resistance to chemicals. Unparallel flexibility, multi-directional. Twofold role: first to restore lost flexural capacity and second to provide resistance to withstand expansive forces.
26. Figure shows impact damage that led to both cross-section and breakage of the spiral ties. Using FRP there is only need to re-form the cross-section and apply bi-directional layers to restore lost tensile capacity. Bonding agents may be required to assure capillary suction of the
27. Though there is no absolute way to eliminate all corrosion on underwater piles, there are some effective measures to control them. Cathodic protection is quit simple and protective coatings are used in vast and expensive structures. The FRP composites have many advantages viz. lightweight, posses high strength and chemical resistance and moreover have incomparable flexibility. Of the various ways of wrapping of FRP composites , transverse wrapping is found to be the easiest. Bi-directional material is the best option. Scaffolding measures during the application .

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ABSTRACT

Piles are structures used to transfer loads from superstructure to the sub surface strata. When the subsurface stratum is water based or if we deal with a hydraulic structure, the piles are to be driven into water and under water strata. Piles used in underwater structures are often subjected to corrosion. There is no absolute way to eliminate all corrosion; but corrosion protection measures are employed to control the effect of corrosion. Corrosion protection can be in different ways according to the environment and other factors. Forms of corrosion protection include the use of inhibitors, surface treatments, coatings and sealants, cathodic protection and anodic protection. The control measures explained in this are Protective coatings, cathodic treatment and application of Fibre Re-inforced Polymer (FRP) Composites.

INTRODUCTION

Corrosion is the destruction of metals and alloys by the chemical reaction with the environment. During corrosion the metals are converted to metallic compounds at the surface and these compounds wears away as corrosion product. Hence corrosion may be regarded as the reverse process of extraction of metals from ore.

Corrosion and in particular corrosion of metal structures, is a problem that must regularly be addressed in a wide variety of areas, for example, in the automotive industry, metal parts are often plated or coated to protect them from road salt and moisture in hopes of increasing their longevity. Indeed, many traditional metal parts are currently being used with polymeric components, which are not only lighter but also more cost effective to produce. But these are generally impervious to electrochemical corrosion often experienced by metals. Even with the proper selection of base metals and well-designed systems or structures, there is no absolute way to eliminate all corrosion. Therefore, corrosion protection methods are used to additionally mitigate and control the effects of corrosion. Corrosion protection can be in a number of different forms/strategies with perhaps multiple methods applied in severe environments. Forms of corrosion protection include the use of inhibitors, surface treatments, coatings and sealants, cathodic protection and anodic protection.

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