Piping Materials – Page 21 – What Is Piping: All about Piping Engineering

Anti Corrosive Coatings on Steel are widely used to protect the pipes from corrosion. The protective coating layer helps the steel material to prevent corrosion and increase the useful life of the material. Anti-corrosion coatings are one of the most effective and economical options for tackling corrosion. Corrosion-resistant anti-corrosive coatings serve the following purposes: Protect metal surfaces from degradation due to oxidation, moisture.Prevents direct contact of environmental chemical hazards.Acts as a barrier from corrosive materials.prolong the structural life along with increasing their efficiency.Provides chemical protection, abrasion resistance, etc. For industries like oil and gas, chemical, petrochemical, infrastructure, marine, power generation, etc., the use of anti-corrosive coatings and linings have become a necessity to safeguard the huge investments in terms of money, property and safety of workers. The demand for high-performance anti-corrosion coatings are increasing day be day. A wide variety of anti-corrosive coatings are available in the market to suit the performance requirements of a specific application. Therefore, the selection of anti-corrosion coatings is not an easy process. Various parameters need to be ensured during anti-corrosive coating selection. Sometimes, the coating manufacturer needs to be consulted for some specific information. Corrosion in the Oil and Gas Industry Corrosion in the Piping and Pipeline Industry is quite common. Corrosion is a loss of material due to “REACTION” with the environment. Physical: erosionChemical: irreversible lossElectro-chemical: electric microcellBiological: bio-fouling Forms of Corrosion Corrosion manifests in different forms as listed below: Erosion: commonly observed in lead-lined vessels; area of the vessel near the impellerPitting: micro holes in the relatively unattacked surfaceSelective leaching: dezincification of Cu-Zn alloyIntergranular: welding or improper heat treatmentStress corrosion: welding, cold work, etc.Crevice corrosion: electrochemical cell in the crevice Points to remember The steel surface must be as clean as possible.The metal surface must not have scratches.The anti-corrosive coating itself must be environmentally friendly. Types of Anti Corrosive Coatings Depending on the materials used, anti-corrosive coating can be categorized into the following types Natural PaintsEpoxyPolyurethaneSynthetic ResinsPlasticsPhenolicCompositesAlkydLining: Fiber Reinforced PlasticsGlass liningGraphiteRubber Again, depending on the anti-corrosive coating application they can be divided into two groups: Anti-corrosive coatings for new pipes, andAnti-corrosion coatings for maintenance and repair work. Specific application dictates the type of anti-corrosion coating to be used. Rubber Lining as Anti-corrosive agent Fig. 1: Typical Anti-Corrosive Lined Pipes Types of Rubber Lining: Natural RubberSBRNeoprene(Polychloroprene)Butyl (isobutylene)Halogenated Butyl – e.g. Chlorobutyl Bromobutyl Applications of Rubber Lining: Neoprene Resistant to acid, abrasion, oil, seawater.High temperature and corrosive service, where natural rubber fails. Butyl Rubber Used for High-Temperature Corrosive service e.g. Reaction vesselsFor Hot and abrasive services Applications Chlor-Alkali PlantPhosphoric Acid PlantDI water plants Fluoropolymer Coatings & Linings Anti-corrosive fluoropolymer coatings offer a blend of high-performance resins and fluoropolymer lubricants. Consisting of a dry film lubricant, fluoropolymer coating generates a smooth, hard, and slick final coating to provide excellent corrosion and chemical resistance. Advantages of Fluoropolymer anti-corrosion Coatings & Linings Anti-corrosion fluoropolymer coatings also provide the following advantages: resistance to gallingnon-wetting surfacereduced frictionnon-stick surfaceelectrical resistance andabrasion resistance.Chemical inertness against nearly all substancesBroad application temperature range (-30oC to 260oC)Very smooth material surface and anti-sticking behaviorPossibility of being electrically conductiveImpact-resistantAbsorbs pressure variations or impactsVibration decreasingInsensitive to UV lightNo softening agents usedWeather-resistant and approved for food and drugs service Because of so many benefits, the application of fluoropolymer coating is extensive. Typical examples of anti-corrosive fluoropolymer coating and lining are PFA - PERFLUROALKOXYFEP - FLUORINATED ETHYLENE PROPYLENEETFE - ETHYLENE TETRAFLUORO ETHYLENEECTFE - ETHYLENE CHLOROTRIFLUORO ETHYLENEPVDF - POLYVINYLIDENE FLUORIDEPP – POLYPROPYLENE Fig. 2: Properties of Fluoropolymers Advantages of High-Build Coatings Drastically reduces permeation through the coating and possible corrosion of the metal substrate.It lowers the metal content of the fluid being handled due to the reduction of permeation, substrate corrosion, and back migration of corrosion products.Extends the life of the coating when exposed to abrasive mediaThick coatings can be repaired by welding if mechanically damaged. Thin coatings (<20mil) must be stripped and recoated if repairs are not possible.Thick coatings operate better under pressure-vacuum cycling than thin coatings.The cost of a thick coating is not directly proportional to its thickness. Longer online performance is achieved at only a small additional cost with high-build coatings. Less maintenance is an important benefit.No welds exist with a high-build coated vessel in comparison to one that is sheet-lined. Welds in sheet-lined vessels are a known point of failure.Used in all chemical processes with hazardous, corrosive, abrasive and-or toxic media.Well established in the chemical, pharmaceutical, and petrochemical industryIdeal in any plant because of their good chemical and physical resistance and long lifetime in service.Absence of sensibility against: -mechanical impact-alternating pressure-vibration-temperature shock-aging Application of High-Build Coatings Typical applications of anti-corrosion high-build coatings are Mixed bedsWater storage tanksPumpsPipingChemical storage tanksValvesChemical day tanksFilter housingsWet bench componentsVacuum de-gasifiersAgitatorsCMP components Anti Corrosive Coating Selection Criteria The parameters that must be considered while selecting a suitable anti-corrosive coating are Chemical exposurePermeability of the coatings to the materials to be processedPressure if handling gaseous materialsPurity, FDA, and USDA requirementsMaximum operating temperatureAbrasives, if presentCostVessel configuration – dimensions, complexityDesired fluoropolymerThickness of liningReparabilityTrack record Anti Corrosive Coatings And Linings thickness selection criterion If the corrosion rate of carbon steel is > 10 mpy (mills per year)-USE THICK LININGSIf the corrosion rate of carbon steel is 25MILS OR 0.635MMTHIN LININGS - < 25MILS OR 0.635MM Coatings-Linings thickness selection criterion Use Thin Lining For Product purityNonstickLocalized corrosion Use Thick Lining for Corrosion preventionPermeation resistance Difference Between Coating and Lining: Coatings Vs Linings In terms of Thickness:Coatings – 10 to 1500 microns (0.01 to 1.5mm)Linings – 3000 to 5000 microns (3 to 5 mm)The coating can be done from outside and inside but the lining is done only inside the pipe.Lining in a pipe means a pipe inside a pipe, but the pipe coating is not the same. Coatings are better than linings with respect to the following: adhesive forcesvacuum applicationheat transferthermal shock Few more useful Resources for you… An Article on Forms of Corrosion Corrosion under insulation: A Presentation Corrosion Protection for Offshore Pipelines Corrosion Monitoring Techniques & Surveys: A short Presentation Guide for Coating Selection for External Bolting to Reduce Corrosion Application of Anti-Corrosive Linings in Oil and Gas Industry Anti-Corrosive Composites for Oil and Gas Industry