Title Modeliranje katodne zaštite na modelu platforme kompleksne geometrije Title (english) Modelling of cathodic protection on the model of platform with complex geometry Author Ema Kovačević Mentor Helena Otmačić Ćurković (mentor)Committee member Helena Otmačić Ćurković (predsjednik povjerenstva)Committee member Sanja Martinez (član povjerenstva)Committee member Igor Dejanović (član povjerenstva)Granter University of Zagreb Defense date and country 2021-09-23, Croatia Scientific / art field, TECHNICAL SCIENCES Abstract Morske platforme su objekti sa stalnom potrebom kontrole integriteta konstrukcije. Izrađene od niskougljičnog čelika te djelomično uronjene u morsku vodu, sklone su koroziji. Jedan od glavnih načina očuvanja takvih platformi je uporaba katodne zaštite. Katodna zaštita se može izvesti na dva načina: metodom narinute struje i metodom žrtvovane anode. Zbog starosti konstrukcije i vanjskih utjecaja koji uzrokuju oštećenje premaza, zaštitu platforme potrebno je obnavljati. Prilikom obnove zaštite, češće se koristi metoda žrtvovane anode zbog manjih zahtjeva struje i jednostavnosti izrade. Za takvu izvedbu, koristi se manje plemenit metal, poput cinka, koji postaje žrtvovana anoda u galvanskom sustavu sa konstrukcijom. Većina morskih platformi su kompleksne geometrije zbog potrebne stabilnosti u uvjetima rada. Ta kompleksna geometrija dodatno otežava postizanje ravnomjerne raspodjele potencijala platforme. U praksi, obnova zaštite platformi komplekse geometrije provodi se grupiranjem i distribucijom anoda oko modela prema potrebi. Međutim, za optimiziranje procesa modeliranja katodne zaštite, važno je poznavati utjecaj distribucije anoda. U svrhu analize realnog slučaja obnove zaštite platforme, izrađen je 120 puta manji model platforme komplekse geometrije. Model je zaštićen premazom te su nanesena oštećenja u skladu sa stvarnim primjerima i starosti platforme. Izabrano je 8 pozicija za promatranje utjecaja kompleksne geometrije i raspodjele potencijala. Na tih 8 pozicija postavljene su referentne elektrode od cinka. Izrađeno je 10 žrtvenih anoda, grupiranih u dvije grupe. Utjecaj hidrodinamike morske vode simuliran je korištenjem pumpe. Na temelju izrađenog sustava, promatran je utjecaj distribucije anoda, udaljenosti anoda i strujanja elektrolita na raspodjelu potencijala i struju katodne zaštite modela platforme. Metodom žrtvovane anode postignuta je adekvatna zaštita modela kompleksne geometrije. Pokazana je jača polarizacija središnjeg dijela modela naprema visokim pozicijama i dnu modela, dok zasjenjenost pozicije nije igra veliku ulogu kod polarizacije. Udaljavanjem anoda od modela polarizacija se smanjila. Bolja raspodjela potencijala postignuta je sa jednom grupom anoda. Strujanje elektrolita uzrokovalo je porast struje zaštite, gdje je veći utjecaj primijećen na sustavu sa jednom grupom anoda. Zaključeno je da je u vodljivom elektrolitu distribucija anoda oko konstrukcije nepotrebna.
Abstract (english) Offshore platforms are facilities with a constant need to control the integrity of structures. Made of low-carbon steel and partially immersed in seawater, they are prone to corrosion. One of the main ways to preserve such platforms is to use cathodic protection. It can be made in two ways: by the impressed current method and by the sacrificed anode method. Due to the aging of the structures and external influences that cause damage to the coating, the protection of the platform needs to be constantly restored. When restoring protection, the sacrificed anode method is used more often due to lower current requirements and ease of fabrication. For such a performance, a less noble metal, such as zinc, is used, which becomes a sacrificial anode in a galvanic system with a structure. Most offshore platforms have complex geometries due to the required stability under operating conditions. This complex geometry makes it even more difficult to achieve an even distribution of platform potential. In practice, the restoration of protection of complex geometry platform is carried out by grouping and distributing the anodes around the model as needed. However, to optimize the cathodic protection modeling process, it is important to know the impact of anode distribution. To analyze the real case of platform protection renewal, a 120 times smaller model of the actual platform of the geometry complex was made. The model was coated with anti-corrosion coating and damage was inflicted in accordance with actual examples and the age of the platform. 8 positions were selected to observe the influence of complex geometry and potential distribution. Zinc reference electrodes were placed at these 8 positions. 10 sacrificial anodes were made and grouped into two groups. The impact of seawater hydrodynamics was simulated by using a pump. Based on the developed system, the influence of anode distribution, anode distance and electrolyte flow on the potential distribution and cathodic protection current of the platform model was observed. Adequate protection of the complex geometry model was achieved by the sacrificial anode method. A stronger polarization of the midpoints of the model relative to the top and bottom of the model was shown, while the shading of the position did not play a significant role. By moving the anode away from the model, the polarization decreased. Better potential distribution was achieved with one group of anodes. Electrolyte flow caused an increase in protection current, where a greater impact was observed on a system with a single group of anodes. It was concluded that in the conductive electrolyte, the distribution of anodes around the structure is unnecessary.
Keywords
odobalne konstrukcije
korozija
katodna zaštita
Keywords (english)
offshore constructions
corrosion
cathodic protection
Language croatian URN:NBN urn:nbn:hr:149:320317 Study programme Title: Chemical Engineering - Graduate study Type of resource Text File origin Born digital Access conditions Access restricted to students and staff of home institution Terms of use Created on 2023-04-14 12:41:11
