Aufklärung von Korrosionsprozessen bei der Erdölverarbeitung mittels Mössbauer- und Röntgenuntersuchung – I. Atmosphärische Destillationskolonnen

Study of the corrosion processes at the primary oil refining by Mössbauer and X-ray investigation – I. Atmospheric distillation columns Samples from zones of intensive corrosion in distillation and stabilization columns of atmospheric crude oil distillation were studied by means of Mössbauer spectroscopy and X-ray diffraction. Qualitative and quantitative composition of the surface layers were established. They were found to consist of sulphides, sulphates, oxides and oxihydroxides of iron as well as sulphur. Sulphide, sulphate, and oxygen corrosion dominate. Secondary physicochemical and chemical transformations of the formed products have importance. The probable mechanism of the corrosion processes taking place is discussed.     

Mikrobielle Werkstoffzerstörung – Schadensfälle und Gegenmaßnahmen für Kunst- und Naturstoffe: Mikrobielle Zerstörung von Kunststoffen

Microbial deterioration of materials – case histories and countermeasures for plastics and organic and natural materials: Microbial deterioration of plastics Large-scale production of synthetic plastics began in the thirties. The versatility of the new materials was enhanced by new processing technologies and above all by designing special formulations tailored to the different fields of applications. Their increasing universal application was, however, also accompanied by growing records of documented microbial attack. The mechanisms of attack have largely been identified. Damage is commonly caused by surface growth, discolourations and changes of mechanical and electrical properties. National and international test standards have been developed to predict the service life of certain plastics or to evaluate the protection afforded by certain biocides. Several standard methods of test are presented and the criteria for evaluation are critically examined. Finally, the activities of the Plastics Project Group are represented, wich has carried out several international co-operative tests to evaluate the reproducibility of the results of different test methods and has worked out recommendations and improvements.     

Mikrobielle Werkstoffzerstörung – Schadensfälle und Gegenmaßnahmen: Anwendung von Mikrobiziden. Mikrobizid-Wirkungsmechanismen

Microbial deterioration of materials – case histories and countermeasures: Application of microbicides – Mechanisms of functioning of microbicides Microbicides are defined as a subgroup of the biocides. Such microbicides are discussed here which are appropriate for the protection of materials, additionally active ingredients for disinfectants and agents able to prevent disturbances and damage caused in industrial processes by formation of algae and slime. The effective use of microbicides presupposes knowledge of the materials and production processes to be protected, of the microbe species responsible for the biodeterioration and of the properties and mechanisms of action of the active agents conditional on their structure. This knowledge enables one to select an appropriate microbicide for the solution to the problem. Different modes of action are described basicly and adjuncted to certain substance classes. It is differentiated between membrane-active and electrophilically active agents and those which are able to form chelates. The differences in mechanisms of action result in different consequences for the application of microbicides.     

Mikrobielle Werkstoffzerstörung – Simulation,Schadensfälle und Gegenmaßnahmen: Untersuchung der Beständigkeit von keramischen Werkstoffen

Microbial deterioration of materials – simulation, case histories and countermeasures: Testing of the resistance of ceramic materials Testing of microbiologically influenced corrosion of ceramic materials by biogenic sulphuric and nitric acid corrosion is well described and applied for constantly moist buildings like sewage pipelines and cooling towers. The complex situation on historical buildings of natural sandstones has not yet been investigated in the laboratory. A double-chamber cabinet and a test system for the simulation of chemically (gaseous pollutants), combined chemically and microbiologically (gaseous pollutants plus nitrifying bacteria) and solely micro biologically (nitrifying bacteria) influenced corrosion of natural sandstone is presented. A high stone moisture was essential for the growth of nitrifying bacteria on test stones. Under optimum conditions a nitrifying biofilm developed on the calcareous Ihrlersteiner green sandstone, reducing the evaporation from the stone surface. Biofilm cells adapted well to high concentrations of gaseous pollutants (1,065 μg/m³ sulphur dioxide, 850 μg/m³ nitric oxide, and about 450 μg/m³ nitrogen dioxide): in the simulated smog atmosphere. The mean metabolic activities of ammonia oxidizers were 11 times and those of nitrite oxidizers 30 times higher than mean values of samples from historical buildings. The microbiologically, influenced nitric acid corrosion alone was 8 times stronger than the chemically influenced corrosion by the simulated smog atmosphere. If sulphur dioxide was added, the microbiologically produced nitrite was removed by chemodenitrification. Thus, the combined attack of nitrifying bacteria and gaseous pollutants did not result in an increased corrosion, but the nitrifying biofilm promoted the formation of gypsum.     

Anwendung der röntgenografischen Verbundanalyse bei der Schadenaufklärung

Application of composite radiographical methods of analysis to the investigation of cases of damage On the strength of numerous examples, it is shown that the combination of the X-ray fluroescence analysis with the X-ray microstructure analysis represents an important aid in investigating cases of damage as the corrosion products are analyzed not only in regard to their composition but also in regard to the type of compound. The following causes of corrosion have been diagnosed in this way: — Sedimentation of catalyst particles and of entrained dissolved products from the boiler water; temperature below condensation point; effects of potassium sulphate and/or aluminium ortho-arsenate or of vanadium compounds from fuel oil; wet cleaning with ammonia water before commissioning a boiler; effect of alkali and alkaline earth oxides on the brick lining of a combustion chamber; deficiency of iron sulphate as a cause of deficient cover layers on brass; effect on galvanized parts of the HCL formed during the combustion of PVC.     

Mikrobielle Werkstoffzerstörung – Schadensfälle und Gegenmaßnahmen für Kunst- und Naturstoffe. Biotransformation und Kompostierbarkeit von Folien

Microbial deterioration of materials – case histories and countermeasures for plastics and natural materials: Biotransformation and cornposting of foils     

Mikrobielle Werkstoffzerstörung – Grundlagen: Grundvorgänge der Korrosion

Microbial deterioration of materials – fundamentals: Basic corrosion processes Microbial growth on metal surfaces induces a number of corrosion reactions which are due to changes in the conditions on the boundary layer. The corrosion systems in question are numerous and damage mechanisms correspondingly manifold. Metallic materials corrode according to known electrochemical mechanisms, whereby microorganisms act indirectly. They produce biofilms which are the cause of concentration cells (oxygen, pH, metal salts) and finally lead to local corrosion effects. Another widespread mechanism is based on the formation of sulphide by sulphide-reducing bacteria which stimulate electrochemical partial reactions. A third large group is attributed to the acid producing microorganisms which attack both metallic and inorganic materials. There is no indication that microorganisms are directly involved in the basic reactions of metal corrosion. The corrosion mechanism of inorganic materials, such as the concrete/sulphuric acid system, is of a purely chemical nature and involves processes, such as binding rupture by ion exchange, solvation, hydrolytic cleavage and chemical conversion. Contrary to this, microorganisms participate directly in the deterioration process of organic materials. For each natural polymer a microorganism exists which is capable of complete or partial decomposition of the polymer, whereby it, or additives (e.g. plasticizers). act as C and/or N sources. Explanations of mechanism are, therefore, transferred to the field of microbiology and physico-chemical interpretation is only partially possible.     

Mikrobielle Werkstoffzerstörung – Biofilm und Biofouling: Bekämpfung von Biofouling in wäßrigen Systemen

Microbial deterioration of materials – biofilm und biofouling: Countermeasures against biofouling in water systems Countermeasures against biofouling include three steps: i) detection, ii) sanitization and iii) prevention of biofouling. The detection has to refer to surfaces. Cell counts in water samples do not reflect site or extent of biofilms. Biocides display only limited value in terms of removal of biofouling layers. First, biofilm organisms are protected against biocides and tolerate 10–1000 fold higher concentrations. Second, water systems usually cannot be kept sterile. Thus, dead biofilms provide nutrients and suitable surfaces for further growth of cells imported with the raw water. Cleaning of a system is an integral part of sanitization and even more important than disinfection. It has to base on a designed strategy. Efficiency control is mandatory, which has to occur on representative surfaces. The prevention of biofouling is frequently achieved by continuously dosage of biocides. This is, however, only possible with suitable raw waters and many failures are reported. Chlorine is still the biocide most frequently used. Reasons of effectivity and environmental protection give rise to other strategies. “Good housekeeping” is recommended as countermeasure. It consists of frequent cleaning, efficiency control, biofilm monitoring, limitation of nutrients, maintenance of high shear forces and a cleaning-friendly design.     

Korrosion unter Erdöl- und Erdgasförderbedingungen bei extrem hohem H2S-Gehalt. Werkstoffauswahl und praktische Bewährung

Corrosion under oil and gas well conditions at extremely high hydrogen sulfide contents. Materials selection and operating performance For the development of the Prinos oil field extensive investigations for selecting the proper materials and inhibitors had to be carried out after it became clear that the gas accompanying the oil had a hydrogen sulfide content of 60%. This required careful simulation of the pressure/temperature oil field conditions in the laboratory. The following problems had to be treated:

• 1 Performance of low strength carbon-manganese steels and inhibitors
• 2 Testing the corrosion resistance of medium strength materials with higher alloy contents
• 3 Behavior of carbon-manganese steels under desulfurization plant conditions (diglycolamine wash)
• 4 Corrosion behavior of coiled tubings used for oil well circulation treatments
• 5 Behavior of high alloy and high strength special materials for fittings and machinery under operating conditions including hydrogen induced cracking environments
• 6 Comparison of laboratory results with specimens taken from production strings after longer operating periods under field conditions.

     

Mikrobielle Werkstoffzerstörung – Biofilm und Biofouling: Biofouling

Microbial deterioration of materials – biofilm and biofouling: Biofouling The undesired deposition of microorganisms and the formation of biofilms is called “biofouling”. In water systems, biofilms are contamination sources for the water phase and support rapid microbial regrowth. Biofilms cover surfaces. In membrane processes, this leads to an increase of the hydraulic membrane resistance. Biofilms are viscoelastic and display a more or less rough surface. Thus, they consume kinetic energy and cause an increased pressure drop when water is pumped. In porous filter media, membrane systems, heat exchangers, water pipelines and on ship bottoms, thus, the energy demand is increased while the performance is decreased. In heat exchangers, biofilms represent a gel layer between medium and surface. This allows only diffusive but no convective heat transport and, thus, decreases the effectivity of the heat transfer process. The loss of performance and product quality as well as by cleaning efforts due to biofouling causes high technical and financial damage. This is increased indirectly by counter-measures such as the application of biocides, because these may promote corrosion processes and contaminate the environment.     

Mikrobielle Werkstoffzerstörung – Biofilm und Biofouling: Die FTIR-Spektroskopie zur Untersuchung von Biofilmen

Microbial deterioration of materials – biofilm and biofouling: Investigation into biofilms by FTIR spectroscopy The investigation of the development and properties of biofilms is difficult because classical microbiology offers only destructive methods apart from microscopical observation. This paper presents the FTIR spectroscopy as a means to investigate microorganisms in biofilms. Furthermore, in completion to taxonomical and genetical methods for the identification of microorganisms, the FTIR analysis provides fingerprint spectra, allowing the rapid characterization of microbial strains. The FTIR-ATR technique can be used for the observation of biofilms forming directly on the ATR crystal. Spectra can be gained non-destructively, in situ and in real time. The method is suitable for fundamental biofilm research as well as for monitoring of biofilm formation, e.g., in an ultrapure water system. It also allows the rapid analysis of deposits on filtration membranes or other surfaces and supports the discrimination between microorganisms, inorganic material or other foulants. The potential of the diffuse reflexion (DRIFT) is emphasized. With the DRIFT method it is possible to investigate rough surfaces or pulverized material and to detect biomass or other surface contaminants. The examples demonstrate that the FTIR spectroscopy holds a powerful potential for biofilm analysis and can be applied in manyfold ways.     

Mikrobielle Werkstoffzerstörung – Schadensfälle und Gegenmaßnahmen: Anwendung von Mikrobiziden. Tebuconazole – ein neues Triazol-Fungizid für den Holzschutz

Microbial deterioration of materials – case histories and countermeasures: Application of microbicides. Tebuconazole

1 Preventol®A 8

– a new triazole-fungicide for wood protection     

Mikrobielle Werkstoffzerstörung – Schadensfälle und Gegenmaßnahmen: Umweltrechtliche Belange

Microbial deterioration of materials – case histories and countermeasures: Legal aspects of environmental protection Biofouling is a natural process. Usually, it does not cause too much harm if taken care of properly. If biofouling is fought by special means, problems may arise. The waste water does not meet the due standards. Sometimes the recipe of the treatment agent is not known. If the treatment causes more problems than it can solve help is needed quickly. Yet, it is advisable to keep one's mind clear. Wrong help can become very expensive. In addition, legal punishment will follow, if environmental legislation is hurt. Damages of the environment will be payed by an insurance company only, if the risk is covered by the insurance contract in advance. The best way to be sure is to have a good lawyer, a good expert in environmental techniques and environmental legislation, a good insurance, and to anticipate possible risks.     

Mikrobielle Werkstoffzerstörung – Schadensfälle und Gegenmaßnahmen für Kunst- und Naturstoffe. Kohlenwasserstoffe

Microbial deterioration of materials – case histories and countermeasures for plastics and natural materials: Hydrocarbons A wide range of bacteria, yeasts and filamentous fungi utilize hydrocarbons as their sole energy and carbon sources. Microbial degradation of hydrocarbons has economic implications when spoilage of crude oils and petroleum products such as fuels, hydraulic oils, lubricating oils, and cutting oil emulsions will occur. As a consequence of microbial infection the oil product changes chemically and functionally and some components may disappear completely. Metabolic products may cause severe corrosion or may be used as substrates by other microorganisms, e.g. sulfate reducers, which for this part will cause corrosion. In consequence of biomass production screens and filters may be blocked and plugging of pores and pipeline-systems may occur. As spoilage can only, occur in the presence of free water, good housekeeping is a prerequisite to prevent microbial hydrocarbon degradation. In cases free water cannot be excluded or removed completely, biocides can he added. The growth of anaerobic bacteria (sulfate reducers) is inhibited by introducing oxygen into the system. Coatings can be used to protect metal surfaces from corrosion.     

Mikrobielle Werkstoffzerstörung – Schadensfälle und Gegenmaßnahmen: Anwendung von Mikrobiziden. para-Chlor-meta-Kresol (PCMK) – Ein klassisches Mikrobizid mit Zukuntt

Microbial deterioration of materials – case histories and countermeasures: Application of microbicides. Para-chloro-meta-cresol (PCMC)

1 Preventol®CMK.

– A classic microbicide with a future     

Mikrobielle Werkstoffzerstörung – Schadensfälle und Gegenmaßnahmen: Allgemeine Schutzmaßnahmen vor biogener Materialzerstörung

Microbial deterioration of materials – case histories and countermeasures: General measures for protection against biogenic destruction of materials Many materials are adversely affected or even destroyed by microorganisms. In the cases where the causes of biogenic damage are known, specific protective measures can be taken. Depending on the material in question, these measures can be of a constructional, physical or chemical nature, and all three procedures are frequently used in combination. Constructional measures are to be found in the “buildings” sector. Examples to be mentioned are water being led off at windows and buildings being ventilated in order to prevent mould invasion in particular. Treating surfaces by applying adhesive coatings or water-repellent products can prevent attack by microorganisms on e.g. wood and metals. Physical measures are also used in protecting buildings. In addition to insulating the building, which then has few bridges of heat, the sorption behaviour of the surfaces and the heat transfer coefficients on the surfaces also influence the growth conditions for microorganisms. Materials with a high sorption capacity have particularly adverse effects on poorly insulated buildings. As chemical protective measures, use is made of preservatives and products for microbistatic treatment and also impregnating agents. These measures are applied in the paint, paper, and wood industries, among others. In addition, the choice of raw materials and the use of “rot-proof” materials in textiles and plastics can reduce microorganism-induced biodegradability and, thus, prolong the life. Not least, on the majority of production sites good production hygiene is urgently necessary as a concomitant measure.     

Möglichkeiten der Bestimmung des Zustandes der Betauung und Befeuchtung der Oberfläche

Possibilities for the determination of the electrolyte formation on surfaces by condensation and moisture particle impact In order to control the presence of electrolyte films on surfaces measuring probes are attached to the piece to be studied and the change of the electrical resistance of the probes is measured. These probes are passive dipoles and form a system of metallic area electrodes separated from each other by a crevice of defined dimensions (geometrical shape and size are adjusted to the particular problem). The electrodes are applied to a support combining high insulation resistance, water resistance, low weight and good thermal conductivity. The probes are connected to an electronic system recording the signals from the individual probes, so that the duration and the frequency of moisture film formation can be determined; the recording strip further enables a differentiation to be made between condensation (dew formation) and direct impact of liquid particles.     

Elektrochemisches Verhalten von Aluminium und Möglichkeiten des Korrosionsschutzes in der Praxis

Electrochemical behaviour of aluminium and possibilities of practical corrosion protection The characteristic passivity of aluminium is shown by potentialcurrent density diagrams of materials AlMg2Mn0.8 and AlMgSi0.5 in seawater and in special hard water. These diagrams indicate the value of the passivity area, which is limited in anodic direction by the pitting potential. In the corrosion-system the pitting potential is influenced by the alloying elements in aluminium and also by the inhibitors in the corrosive medium. Zinc in aluminium diminishes the passivity area and sodium chromate in the special hard water enlarges the passivity area. Comparison of the corrosion behaviour of AlMg2Mn0.8 and high purity aluminium with respect to only the pitting potential does not permit conclusions to be drawn about the corrosion probability since pitting corrosion can only occur when a critical value is exceeded. The corrosion-sensitive aluminium-recycling material can be cathodically protected by reducing the potential below this value with help of galvanic anodes.