CORROSION

1. CORROSION İrem ÖZDEMİR52072461142

2. Reinforcedconcrete is one of themostcommonmaterialsusedbytheconstructionindustryallovertheworld. Owingtothewidevariety of applications, Reinforcedconcrete is usedforconstruction of transportationinfrastructuresuch as bridges, tunnels, andharbourstructures. It is alsousedforoffshoreplatformsand a widerange of publicandprivatebuildings.

3. Owingtothewidevariety of applications, reinforcedconcretearesubjectedto a range of exposureconditionssuch as CORROSION. Corrosion is theloss of massthatoccurs as a result of electrochemicaleffects.

4. Reinforcementcorrosion is one of the main durabilityproblems. High durabilityrequirements is not alwaysachieved in practiceduetowhichcorrosion of reinforcement in concrete is one of the main causeof deterioration in RC structures.

5. Whentheconcrete is firstpoured, it wrapsthereinforcementandprotectsagainstrust. Thehigh alkaline environment in concreteadheresfirmlytothereinforcementsteelandforms a film topreventcorrosion.

6. However, duetofactorssuch as vibration, vibration, mechanicalfatigueandexternalconditions, microscopiccracksoccur in theconcreteandgraduallygrows, causingmoisture, corrosivesubstancesandgases in theexternalenvironment, CO2, leakage of flueandexhaustgases in theair.

7. Forsuchreasons, thereinforcement is rusted, itssection is reducedanditsstrengthdecreases. Components formingtheconcretesometimescausereaction. Suchinternalcorrosion can alsocausecorrosion of thereinforcement. Theresultingrusting can increasethevolume of iron, causingcracking in concrete.

8. REFERENCES • Dhawan S., Bhalla S., Bhattacharjee B. (2014),»ReinforcementCorrosion in ConcreteStructuresand Service Life Predictions», 9th International Symposium on Advanced ScienceandTechnology in ExperimentalMechanics, 1-6 November, 2014, New Delhi, India<https://www.researchgate.net/publication/267636737_Reinforcement_Corrosion_in_Concrete_Structures_and_Service_Life_Predictions_-_A_Review> • Tahershamsı M.(2016),«StructuralEffects of ReinforcementCorrosion in ConcreteStructures», Gothenburg,Sweden<http://publications.lib.chalmers.se/records/fulltext/239743/239743.pdf> • https://eduardodseng.wordpress.com/2013/12/03/corrosion-of-steel-in-concrete/

9. CORROSION PRECAUTION TO RESTRICT

10. * Concrete water-cement ratio is aspecially important in determining the rate of ingress of water ,and therefore dissolved salts , into concrete. • * Some admixtures and additives are very effective in reducing further the permeability of concrete.

11. *Theeffect of aggregates on thepermeability of concrete is generallytoincreaseit.Becasetheaggregatesoccupyapproximatelythreequarters of thevolume of concrete , andtheirpermeabilities can be as much as 1000 timesgreaterthanthat of highqualityportlandcementpaste , theyhave a profoundeffect on theprotectionconcreteofferstoreinforcingsteelagainstcorrosion.

12. *Woks has shown the extremely important effects of coveran and low water-cement ratios in resisting the ingress of the chloride ion into concrete.The reason that 1 inch of cover was relatively ineffective in resisting chloride intrusion is considered to be due to the fact that  ¾ inch (19 mm) maximum size aggregate was used.Because of its intrinsically higher permeability and the high permeability of the paste adjacent to some aggregates , one large aggregate particle can easily "short circuit" the distance between the concrete surface and the steel. This explains why two inches of cover is so much more effective than one , and three is , comperatively , little better than two.

13. *Other method of decreasing the permeability of the concrete is synthetic latex admixtures. It provides effective resistance against moisture and chloride penetration. • *Latex redce the permeability of concretein two ways.The physical presence of a lattice of latex within the concrete presents a more torturous route to water attempting to penetrate the concrete. And the reduction in mix water , made possible by the solids portion of the latex that imparts the workability of its own to the concete , results in lower permeability due to a decreased waterr-cement ratio paste.

14. * Anothermethod of greatlyreducingtheamount of waterrequiredtomakeconcreteworkable is theaddition of a high-rangewaterreducer (HRWR). • *Incombination HRWR andsilicafume , concrete can be proucedwithpermeabilities as low as that of latex-modifiedconcete. Theuse of othersupplementarycementingmaterialssuch as flyashandgroundgranulatedblast-furnaceslagreducethepermeability of concrete.

15. *Another additive available as an anti-corrosion agent is calcium nitrite. This material acts as an anodic passivating inhibitor , to increase the chloride threshold level for corrosion initiation. Several papers suggest using a combination of this calcium nitrite and silica fume.The philosophy was that the silica fume would slow the entry of water and calcium nitrite would slow the corrosion rate after the chloride concentration reached the threshold level at the steel.

16. *A different approach to the prevention of penetration of water and dissolved salts into concrete is to apply a surface sealer after the concrete has hardened. • *Another approach to preventing corrosion is to coat the steel.Zinc has been used for this purpose and it must be used on all the steel within the stucture rather than only that which is expected to become anodic.

17. *A morewidelyusedmaterialtousefosurfaceprotection of thesteel is fusion-bondedepoxy. *Earlyworkshowedalthoughtheepoxytypically has smallholes in thefinishedcoating , andthecoating can be damagedbyroughhandlingorbending of thebars , it can do a verygoodjob of protectingthesteel , particularlyifallthesteel in thestructure is coatedandthnumber of holesareminimized.

18. REFERENCES • Significance of TestsandProperties of ConcreteandConcreteMakingMaterials •                                                                         Joseph F. Lamond •                                                                         James H. Pielert

19. Umut Can BOZACI 58645345178 CORROSION INHIBITING AGENTS

20. A corrosioninhibitor is a chemicalsolventwhich is applied in a particularenvironmentthatsignificantlydecreasesthecorrosion rate of elements (especiallymetals) exposedtothatsurroundingenvironmenti.e. airandwater. • Corrosion inhibitors are added to prolong the service life of reinforced concrete, primarily acting at the steel surface.

21. These substances should not be harmful to concrete. thus, the inhibitors are added to the fresh concrete with the mixing water and are present at the steel surface from the beginning. • Corrosion inhibitors as admixtures can thus be, in principle, an additional means of prevention by acting in two ways: prolonging the initiation time and reducing the corrosion rate in the propagation phase

23. Types Of CorrosionInhibitors • AnodicInhibitors • CathodicInhibitors • Mixed Inhibitors • VolatileCorrosionInhibitors

24. AnodıcInhıbıtors • This type of inhibitors forms an insoluble protective film on anodic surfaces to passivate the steel. An anodic inhibitor shifts the potential to the passivation zone causing the formation of a thin passive film on the anodic sites, which increases the potential of the anode and decrease the corrosion in rate. There are two types of passivating inhibitors; • Oxidizing anions, such as chromates, nitrates, and nitrites, passivate the steel in the absence of oxygen. • Nonoxidizing ions, such as phosphate, tungstate, and molybdates, require the presence of oxygen to passivate the steel.

25. Anodic inhibitors are effective only when present in sufficiently high concentrations. Typically, the concentration required is determined by the level of chloride present in the environment in which the steel is exposed. • The most commonly used anodic inhibitor for concrete is calcium nitrite. Calcium nitrates show similar inhibiting properties in concrete. • Some anodic inhibitors, such as nitrites, cause accelerated corrosion and pitting if the concentration drops below the threshold/critical level. • Nitrates, benzoates, chromates, molybdates, and orthophosphates are used as anodic inhibitors.

26. CathodicInhibitors • Cathodic inhibitors slow down corrosion by reducing the rate of cathodic reactions in the corrosion environment. • A cathodic inhibitor causes the formation of insoluble compounds precipitating on the cathodic sites in the form of a barrier film. These inhibitors are called precipitation inhibitors.

27. Zinc and magnesium salts are cathodic inhibitors that form precipitates of zinc hydroxide and magnesium hydroxide at the cathode. • Cathodic inhibitors are not as effective as anodic inhibitors, but they are not likely to cause pitting.

28. Mixed Inhibitors • Mixed inhibitors quash both the anodic and cathodic reactions, and they reduce the corrosion rate by forming a thin protective hydrophobic film on entire surface of the metal through adsorption mechanism. • The material with the hydrophobic group that has polar groups, such as N, S, and OH, is effective.

29. These inhibitors are called adsorption or film-forming inhibitors. The effectiveness of the film depends on the chemical composition, molecular structure, and their affinities for the metal surface. The strength of the bond is the dominant factor for organic inhibitors. • Organic inhibitors can also act as pore blockers, reducing the permeability of the concrete. Amines and amino alcohols are the commonly used mixed inhibitors, which displace the chloride ion and form a durable passivating film.

30. VolatileCorrosionInhibitors • Volatile Corrosion Inhibitors (VCI) are products moved in a closed atmosphere to the section of corrosion by volatilization from a source. • In boilers, volatile basic compounds, such as morpholine or hydrazine, are carried with vapor to stop corrosion in the condenser tubes by counterbalancing acidic carbon dioxide or by changing exterior pH towards less acidic and corrosive rates. • In closed confined spaces, such as shipping containers, VCI products such as VCI paper VCI bags or VCI rust removers are used. • Qualities of a VCI product depend on the volatility of its compounds; Quick action sequence high volatility while providing protection requires low volatility.

31. Effect of anodic, cathodic, and mixed inhibitors in concrete • Corrosion of steel in concrete structures is the primary concern when the structures are exposed to the coastal marine environment. The use of corrosion inhibitors can delay the onset of chloride-induced corrosion, prolong the time to initiation of corrosion, and thereby reduce the corrosion rate. • Calcium nitrite is the most commonly used anodic corrosion inhibitor for reinforced concrete. This inhibitor is a passivating inhibitor, which forms a passive film on the surface of steel and significantly reduces the corrosion rate of steel in chloride-contaminated concrete. • The inhibitive action of steel with calcium nitrite is as follows: Amines-, alkanol amines-, and carboxylate-based mixed inhibitors are mostly used in reinforced concrete.

32. FIELDS OF APPLICATION • • acidstimulationjobs, • • coolingsystems, • • drillingmuds, • • oilproductionunits, • • oilstoragetanks, • • protection of pipelines, • • refineryunits, • • scale removal treatments using acids, • • steamgenerators, and • • technologicvessels.

33. REFERENCES • https://www.sciencedirect.com/science/article/pii/B978008100693100014X • https://www.sciencedirect.com/science/article/pii/B9780444627223000148 • https://www.sciencedirect.com/science/article/pii/B9780128037348000060

34. FIBRE REINFORCED PLASTIC(frp) MATERIALS

35. Composite plastics aretypes of plastics that result from bonding two or more homogeneous materials with different material properties. • Main aim isto derive a final product with certain desired material and mechanical properties.

36. FIBRE • Providestrengthandstiffness. • Theirquality,orientationandshapeaffectthe final product. • Forms; shortfibers,choppedfibers,longfibers,wovenfibers. • MATRIX (Resin) • Coatsthefibres. • Protectsthefibresfromabrasion. • Transfer stressesbetweenthefibres. • Forms;thermosetresins(mostcommonforstructuraluses) andthermoplasticresins.

38. Widerange of FRP productsareavailable • Plates (RigidStrips) • Sheets (FlexibleFabric) • Rods • Thefibrescould be; • Carbon • Glass • Aramid

39. ADVANTAGES • Corrosionresistance. • Reducedinstallation time andcost. • Lowmaintenancerequirements. • Lowthermalconductivity.

40. DISADVANTAGES • High temperature is a seriousconcern. • Higherrawmaterialcost.

41. REFERENCES • https://www.sciencedirect.com/science/article/pii/S1876610217357016  • https://www.sciencedirect.com/science/article/pii/S1877705815011145