Stainless steels were developed in the early 20th century and are used where both the mechanical properties of steels and corrosion resistance are required. There is continuous research to allow stainless steel components to be produced in a more economical way and be used in more harsh environments. A necessary component in this effort is to correlate the service performance with the production processes. The central theme of this thesis is the mechanical grinding process.  This is commonly used for producing stainless steel components, and results in varied surface properties that will strongly affect their service life. The influence of grinding parameters including abrasive grit size, machine power and grinding lubricant were studied for 304L austenitic stainless steel (Paper II) and 2304 duplex stainless steel (Paper I). Surface integrity was proved to vary significantly with different grinding parameters. Abrasive grit size was found to have the largest influence. Surface defects (deep grooves, smearing, adhesive/cold welding chips and indentations), a highly deformed surface layer up to a few microns in thickness and the generation of high level tensile residual stresses in the surface layer along the grinding direction were observed as the main types of damage when grinding stainless steels. A large degree of residual stress anisotropy is interpreted as being due to mechanical effects dominating over thermal effects. The effect of grinding on stress corrosion cracking behaviour of 304L austenitic stainless steel in a chloride environment was also investigated (Paper III). Depending on the surface conditions, the actual loading by four-point bend was found to deviate from the calculated value using the formula according to ASTM G39 by different amounts. Grinding-induced surface tensile residual stress was suggested as the main factor to cause micro-cracks initiation on the ground surfaces. Grinding along the loading direction was proved to increase the susceptibility to chloride-induced SCC, while grinding perpendicular to the loading direction improved SCC resistance. The knowledge obtained from this work can provide a reference for choosing appropriate grinding parameters when fabricating stainless steel components; and can also be used to help understanding the failure mechanism of ground stainless steel components during service.

Stainless steels were developed in the early 20th century and are used where both the mechanical properties of steels and corrosion resistance are required. There is continuous research to allow stainless steel components to be produced in a more economical way and be used in more harsh environments. A necessary component in this effort is to correlate the service performance with the production processes. The central theme of this thesis is the mechanical grinding process.  This is commonly used for producing stainless steel components, and results in varied surface properties that will strongly affect their service life. The influence of grinding parameters including abrasive grit size, machine power and grinding lubricant were studied for 304L austenitic stainless steel (Paper II) and 2304 duplex stainless steel (Paper I). Surface integrity was proved to vary significantly with different grinding parameters. Abrasive grit size was found to have the largest influence. Surface defects (deep grooves, smearing, adhesive/cold welding chips and indentations), a highly deformed surface layer up to a few microns in thickness and the generation of high level tensile residual stresses in the surface layer along the grinding direction were observed as the main types of damage when grinding stainless steels. A large degree of residual stress anisotropy is interpreted as being due to mechanical effects dominating over thermal effects. The effect of grinding on stress corrosion cracking behaviour of 304L austenitic stainless steel in a chloride environment was also investigated (Paper III). Depending on the surface conditions, the actual loading by four-point bend was found to deviate from the calculated value using the formula according to ASTM G39 by different amounts. Grinding-induced surface tensile residual stress was suggested as the main factor to cause micro-cracks initiation on the ground surfaces. Grinding along the loading direction was proved to increase the susceptibility to chloride-induced SCC, while grinding perpendicular to the loading direction improved SCC resistance. The knowledge obtained from this work can provide a reference for choosing appropriate grinding parameters when fabricating stainless steel components; and can also be used to help understanding the failure mechanism of ground stainless steel components during service. / <p>QC 20160203</p>

Varje år lägger processindustrin världen över 1.372*109 dollar på kostnader kopplade till korrosion. En stor del av denna summa går till korrosion under isolering (CUI). De stora utgifterna kring CUI kommer ifrån avisoleringen av för den visuella inspektionen som måste utföras inom specifika intervall enligt lag. Vid denna inspektion kläs rören av och isoleringen kasseras, vilket leder till stora materialkostnader. Då rörgatorna ofta ligger på svåråtkomliga ställen blir ställningen samt arbetartimmarna de sista stora faktorerna kring CUI hantering. Efter inspektioner uppmärksammas ofta att en stor del av rören varit opåverkade av korrosion. Ifall man kan påvisa att det inte finns någon skäl till misstanke av CUI behöver man inte alltid riva isoleringen. I detta finns det en besparingspotential som redovisas i denna rapport. Då olika anläggningar har en stor variation i sin budget redovisas besparingspotentialen för en låg budget samt en hög budget. Den låga budgeten är antagen att vara 0.35 miljoner per kilometer rör och den höga 2 miljoner per kilometer rör. Det är antaget att 10% av isoleringen kan bevaras med vissa källor säger att upp till 50% av isoleringen kan bevaras. För båda resultaten hinner CUI sensorn betala av sig själv inom de första åren. En andra del som undersöks i denna rapport har med svårigheten kring CUI sensor kontra andra metoder för att lokalisera CUI. Med en CUI sensor kam man inte få ett konkret svar på vart eller om korrosion finns. CUI sensorn mäter av omgivningstemperatur, relativ luftfuktighet alternativt närvaro av vatten men inte närvaron av korrosion. De parametrar som CUI sensorn avläser behöver tolkas om till en sannolikhet för korrosion. Denna sannolikhet representeras på en 1 - 5 skala och baseras på korrosionshastighet, tjocklek på röret samt trycket. Denna lägst nivån på denna skala är efter 0−3 år av blöta rör, den andra nivån 3−6år, den tredje 6−9år, den fjärde 9−12 och den femte allt över 12år.

The Electrochemical Noise Method (ENM) monitors the small potential and current fluctuations that occur naturally in electrochemical cells. It is the least intrusive of all electrochemical techniques in common use. This work uses the Electrochemical Noise Method to investigate the corrosion protection afforded by organic coatings. A parameter called Noise Resistance (Rn) is derived from an Ohm law relationship using the potential noise (Vn) and current noise (In) values. The noise on the current and potential data sets is calculated as the standard deviation value. The work is divided into three areas. The first looked at coating systems in the intact state on the substrate. In general this part of the work has corroborated previous work where Rn values of >l x 10^7 ohms-cm^2 indicated protection of the substrate, correlating with DC resistance values of the coating. The second area of work investigated scribed coatings on the substrate. An important property of organic anti-corrosive coatings is the ability to protect the substrate at a break in the coating. In the scribed work the level of protection afforded at exposed metal by the coating was related to the Noise Resistance value. The third area of this investigation looked at novel ENM techniques to investigate organic coatings. Detached intact coatings were examined in a “U” tube test cell that can be used to simulate different conditions that may be encountered in service. Also a new technique was devised for obtaining ENM data from corrosion cells, this does not require the two separate substrate elements necessary for the more established methodology. The new technique has been called the Single Substrate (SS) technique to reflect this useful property. The technique could be used for in-situ monitoring of structures and it could be adapted for investigation of other situations such as reinforcement bars in concrete

No description available.

To enable improvements in the development of anti-corrosive coatings quick methods of evaluation are required and several are available which are both qualitative and quantitative. This investigation reviews both types of method, the first in the form of traditional salt spray exposure and the second in the form of electrochemical techniques. The emphasis in the experimental work reported here is on the Electrochemical Noise Measurement (ENM). ENM has been used to monitor coatings under immersion conditions, the aim being to assist a paint company develop a set of more environmentally friendly coatings. The immersion test has also incorporated a temperature cycle which proved effective at separating ‘good’ coatings within a short timeframe. Results showed good correlation between ENM and salt spray testing. Work is also reported which was done with the aim of making the ENM method more practically useful. The standard configuration (‘Bridge’) requires two separate specimens which is unattractive for site work. The Single Substrate (SS) arrangement was developed to get around this problem but this still requires the metal to be connected to the measuring instrument. This is avoided in the most recent development which needs No Connection to Substrate (NOCS). Results are given for immersed samples monitored using the ENM NOCS arrangement and compared with the standard ‘Bridge’ method and DC resistance. Results are also presented using sets of different electrodes (platinum, calomel and silver/silver chloride). This preliminary work has shown that the NOCS method holds great promise. In the laboratory Electrochemical Impedance Spectroscopy (EIS) is also commonly employed to assess the performance of anti-corrosive coatings. Concluding this work a comparison of the ENM and EIS techniques was undertaken on a set of laboratory samples. Results showed that both methods had the ability to rank the performance of coatings. However ENM’s advantages (as outlined above) were confirmed

In this study, the corrosion resistance of three different stainless steels (304, 316 and 309) towards eutectic chloride salts is investigated. The performances of two materials to reduce the corrosion of the steels are examined: zirconium as sacrificial anode and an Al2O3 coating deposited by flame spraying. Samples are submitted to a 24 hours corrosion test at 700°C in air. The samples are characterised by weight analysis, SEM observations and EDX analysis of their surface and cross-section. The corrosion resistance of the stainless steels is not improved by adding Zr rods in direct contact with the steel, rather decreased in the areas where the rod laid. However, in these conditions, stainless steel 316 has the best resistance to highly corrosive chloride salts. The Al2O3 coating is too porous and penetrated by the salt, the steel underneath is corroded. Nevertheless, some alumina remains intact after the corrosion test, because of the high inertness of the ceramic. The presence of O2 most certainly accelerated the corrosion mechanism studied here.

Corrosion is a global problem which leads to both economicalct on the environment as well as other negative social and ethical aspects. Sodra Cell Monsteras, one of the largest producer of pulp in the world, suffers from corrosion problems in their evaporation plant. Problems with corrosion can be handled with an effective material selection process, where suitable materials for specific conditions is discovered. The purpose with this report is to investigate the evaporation plant at Sodra Cell and its specific conditions, including environment and temperature. Also to investigate different types of corrosions common in pulp mills and how these can be prevented, as well as how materials behave under corrosive circumstances. The information is later to be used in a detailed material selection process, which is handled in this report but also should work as a foundation for Sodra Cell Monsteras for future material selections. The material selection process in this report is performed according to Ashby's method, with CES Edupack as a supporting tool. The duplex steels, especially EN 1.4485 and EN 1.4362, showed to be the best suitable materials. However, to do a fair judgment and to choose one material, one should do a complete cost efficiency analysis, as well as decide a specific required pitting resistance equivalent number (PREN). / Korrosion ar ett globalt problem som leder till både ekonomiska förluster, negativ miljöpåverkan samt andra negativa sociala och etiska aspekter. Södra Cell Mönsterås, en av världens största producenter av pappersmassa, har problem med korrosion i sin indunstningsanläggning. Korrosionsproblem kan lösas genom att ha en effektiv materialvalsprocess där rätt material för specifika förhållanden och ändamål används. Syftet med den här rapporten är att undersöka vilka specifika förhållanden som råder i Södra Cells indunstningsanläggning, däribland miljö och temperatur. Men även att undersöka vilka olika korrosionstyper som vanligen förekommer i massaindustrin, hur dessa kan förhindras samt hur olika material beter sig under korrosiva förhållanden. Informationen ska kunna användas som underlag i en utförlig materialvalsprocess, som även hanteras i denna rapport men kan även fungera som en grund för Södra Cell Mönsterås framtida materialval. Materialvalsprocessen i denna rapport är utförd enligt Ashbys metod, med CES Edupack som ett hjälpmedel. Det visar sig att Duplexa stål, speciellt EN 1.4485 samt EN 1.4362 är material som lämpar sig bäst för användning i den korrosiva miljön i indunstningsanläggningen. För att kunna göra en rättvis bedömning och välja ut ett av dessa material, bör en fullständig kostnadsanalys utföras, samt att det bör klargöras vilket specifikt värde för "pitting resistance equivalence number" (PREN) som krävs.

In this project a novel chitosan-stearic acid (CS-SA) coating with bee-pollen microcapsules for encapsulation of 2-mecraptobenzothiazole (MBT) as a waterborne formulation for a biocompatible corrosion protection coating was developed and the coating properties was analyzed. Hydrophobic stearic acid (SA) was crosslinked with via a carbodiimide reaction to form micelles and is assembled on the bee- pollen grains and the chitosan matrix was further self-crosslinked using glutaraldehyde (GA). Stearic acid was used to hydrophobically interact with modified pollen and with further crosslinking with the chitosan, which was proven successful by FTIR results. The encapsulation of anticorrosive agent MBT into pollen was successful and examined by UV-Vis spectroscopy, however, the pollen cannot form a fully stable formulation with the chitosan micelle matrix, partially due to its relatively big size (ca. 20 μm), causing problems with forming a proper barrier protection. The size of the grains and the interference of the carbodiimide crosslinking is the most severe problems with the pollen microcapsules. Therefore, no further testing of the corrosive properties could be done, which requires a dense and stable coating to sustain in salty water for the whole measurement period. As the reference coatings without pollen provided much more promising results, especially when crosslinked with GA, the conclusion is that the reactivity of the pollen is proven difficult to crosslink, and choosing a proper size of a microcontainer and the appropriate encapsulation method in the binder matrix is vital and important for developing a corrosion protective coating. / Detta projekt bygger på framställningen och analysen av en tidigare outforskad chitosan-stearinsyra (CS-SA) färg med bi pollen som mikrokapslar för inkapsling av 2-mercaptobenzothiazole (MBT) som en vattenlöslig och biokompatibel anti-korrosions färg. CS-SA var tillverkat med en carbodiimide reaktion för att bilda miceller som ska omslutna pollenkornen, och även ett försök med vidare tvärbindning mellan chitosanen med glutaraldehyde (GA) gjordes. Stearinsyra fick interagera hydrofobiskt med den modifierade pollen och tvärbindes sedan med chitosan, som visade sig vara lyckad med hjälp av FTIR analys. Enkapsuleringen av MBT visade sig med UV-Vis spektroskopi vara lyckad, dock på grund av pollens stora korn (ca 20 μm) orsakade problem med att bilda en stabil barriär mot omgivningen. Storleken av pollen och dess reaktivitet med carbodiimide tvärbindningen är de mest allvarliga problemen med pollen som mikrokapslar, och därav gjordes inga vidare tester av korrosions egenskaperna då detta kräver en täckande och stabil film genom hela mätningen. Då även referensfärgen som gjordes utan pollen gav avsevärt mycket bättre resultat i det avseendet är slutsatsen att reaktiviteten av pollen gör det problematiskt att tvärbinda med chitosan och valet av en kapsel av rätt storlek och hur den inkapslar är avgörande för att utveckla en bra korrosionsskyddande färg.

Corrosion is a mechanism that highly reduces the lifetime of metals in different environments, especially in water or moisture environment. The worldwide maintenance cost due to corrosion is estimated in billions of dollars per year, and actual solutions in terms of coating usually contains toxic or environmentally harmful species. With an always increasing restriction by environmental restraints and regulations, a sustainable solution is urgently needed. Chitosan, easily obtained from chitin, the second most abundant biopolymer on earth, can be the solution to many problems. Crustacean shell waste is one of the major sources of chitin. Its resource efficiency, biocompatibility, and versatile physicochemical properties for chelation and crosslinking make chitosan a promising candidate as matrix material for biobased anticorrosive application. The purpose of the Master Thesis is to combine the properties of chitosan with the high porosity of bee pollen as anticorrosive agent carrier to obtain a fully sustainable solution for anticorrosive protection. The objective of this very ambitious project is to produce a composite material with a triple action: anticorrosive protection of metal surfaces, self-healing property of the coating and anti- biofouling activity. Results show that a biopolymer composite in forms of suspension or coatings with all desired components could be achieve. Specifically, a biopolymer nanocomposite composed of chitosan matrix, embedded with pollen grains that were loaded with anticorrosion agent 2- mercatobenzothiazole (MBT) in advance, and with zinc oxide nanoparticles have been produced. The physicochemical characterization of the biopolymer composite and its coatings, as well as electrochemical impedance spectroscopy (EIS) measurements on stainless steel plate with such coatings, suggest that a uniform and compact coating is obtained. Despite its good hydrophobicity with maximum contact angle 134.32 ± 3.84° with top coating, the chitosan nanocomposite coating is still permeable to water, partially because of the relatively big size of pollen (ca. 20 μm) that introduces gaps and interferes integrity of the coating. Therefore, a full immersion corrosion resistance is not achieved. In conclusion, phase transfer of hydrophobic pollen into hydrophilic chitosan matrix, MBT loading in pollen, ZnO encapsulation in chitosan, as well as crosslinking of chitosan, were successfully carried out. A coating based on such biopolymer nanocomposite is prepared on stainless steel and investigated on its anti-corrosion property. Future work will be choosing a proper sized pollen as a microcontainer to enhance the integrity of the coating, and eventually endow the coating with the three-in-one function, i.e., anticorrosion, antimicrobial, and self-healing. / Korrosion är en mekanism som kraftigt reducerar livslängden för metaller i olika miljöer, särskilt i vatten- eller fuktmiljö. De globala underhållskostnaderna på grund av korrosion uppskattas i miljarder dollar per år, och faktiska lösningar med avseende på beläggning innehåller vanligtvis giftiga eller miljöfarliga arter. Med en ständigt ökande begränsning genom miljörestriktioner och bestämmelser krävs det en hållbar lösning. Kitosan, den näst vanligaste biopolymeren, kan vara lösningen på många problem. Skaldjuravfall är en av de viktigaste källorna till kitosan. Dess resurseffektivitet, biokompatibilitet och mångsidiga fysikalisk-kemiska egenskaper för kelering och tvärbindning gör kitosan till en lovande kandidat som matrismaterial för biobaserade antikorrosiva applikationer. Syftet med denna masteruppsats är att kombinera egenskaperna hos kitosan med den höga porositeten hos bipollen som antikorrosivt medel för att erhålla en helt hållbar lösning för korrosionsskydd. Målet med detta mycket ambitiösa projekt är att producera ett sammansatt material med en tredubbel verkan: korrosionsskydd för metallytor, självhelande egenskap hos beläggningen och anti- biobeväxningsaktivitet. Resultaten visar att en biopolymerkomposit i form av suspension eller beläggningar med alla önskade komponenter kan uppnås. Specifikt har en biopolymer-nanokomposit sammansatt av kitosanmatris med inbäddade pollenkorn, som i förväg packats med antikorrosionsmedlet 2-mercaptobenzotiazol (MBT) och med zinkoxid-nanopartiklar, producerats. Den fysikalisk-kemiska karakteriseringen av biopolymerkompositen och dess beläggningar, liksom elektrokemiska impedansspektroskopimätningar (EIS) på rostfri stålplåt med sådana beläggningar tyder på att en enhetlig och kompakt beläggning erhålls. Trots sin goda hydrofobi med maximal kontaktvinkel 134,32 ± 3,84° med toppbeläggningen, är nanokompositbeläggningen av kitosan fortfarande permeabel för vatten, delvis på grund av den relativt stora storleken hos pollen (ca. 20 μm) som introducerar luckor och stör integriteten hos beläggningen. Därför uppnås inte en fullständig immersionskorrosionsbeständighet. Sammanfattningsvis genomfördes fasövergång av hydrofobt pollen till hydrofil kitosanmatris, MBT-packning i pollen, ZnO-inkapsling i kitosan, samt tvärbindning av kitosan med framgång. En beläggning baserad på sådan biopolymer-nanokomposit framställs på rostfritt stål och undersöks med avseende på dess korrosionsegenskaper. Framtida arbete kommer att bestå i att välja en lämplig storlek av pollen som en mikrobehållare för att förbättra beläggningens integritet, och så småningom förse beläggningen med tre-i-ett-funktionen, dvs.antikorrosion, antimikrobiell och självhelande.