The paper deals with corrosion degradation of gas pipeline. Pipelines play very important role as means transporting gas media over long distances from producers to end-users. Gas pipelines present a risk of potential corrosion degradation that can result in their failure. Corrosion on internal surfaces of steel pipes takes place in CO2, H2S, H2O and chloride environment. Degradation of steel results in loss of mechanical properties, reduction in thickness and ultimate perforation and failure. Corrosion is the electrochemical process that involves the fl ow of electrical currents on a micro or macro scale. For corroding steel, the anodic and the cathodic reactions produces the electrochemical cell. Corrosion protection of internal pipeline surface is based mainly on chemical composition of gas and the use of inhibitors. Corrosion protection of the external steel surface of the product line involves coatings and cathodic protection.

The purpose of this study was to investigate (simulation of environment for salt treatment of roads in winter and the simulation of the environment of condensed exhaust gas) the galvanic corrosion phenomena which can exist in the construction coupling of cars. The electrochemical behaviour of the hot dip galvanized steel and aluminium alloy, stainless steel and aluminium alloy and stainless steel and silumin which were investigated by electrochemical methods in 3 % NaCl solution and in SEG solution. The open corrosion potential measurement was used to obtain the values of the potential for each couple. The measurement showed a greater bimetallic risk for hot dip galvanized steel with aluminium alloy, where there was ΔESCE > 500 mV and this couple is not suitable either for use in aggressive environment. Calculation of the rate of corrosion attack results from the determination of corrosion currents as measured by Taffel and Evans. The extent of corrosion damage was analysed by means of a light microscope. Keywords: bimetallic; aluminium alloy; stainless steel; silumin; exhaust gas; corrosion potential; electrochemical method;

The paper deals with the corrosion properties and corrosion resistance of aluminium alloys types of AlCu (EN AW 2017), AlMgSi (EN AW 6012) and AlZn (EN AW 7075) with heat treatment T3 (solution treatment, forming and natural aging). The basic corrosion characteristics were quantified by measurement of corrosion potential measured against the saturated calomel electrode and weight losses of exposed samples in the environment of distilled water and in solution SARS. The samples of aluminium alloys were immersed in above-mentioned environments for one minute for a period of six months. Furthermore, an extra evaluation of corrosion of exposed aluminium samples was carried out by means of metallographic analysis. The exposed sample surfaces were evaluated using a microscope.

The paper deals with corrosion damage to steel pipes which were a part of the indirect cooling circuit of gas cleaning. The pipes were made from steel ASTM A106 Gr.B. The outer surface of pipes of the inside part of the circuit was affected by flue gases with mean temperature of approximately 1200 °C. The pipes of the outside part of the circuit were exposed to outer environment with mean temperature of about 25 °C. The cooling water flowing in these pipes had mean temperature of about 20 °C and contained a corrosion inhibitor based on zinc chloride (with addition of hydrochloric acid, phosphoric acid and PBTC). Flow rate of cooling water was 3700 m3/h, its total volume 1500 m3, and the pressure of cooling water was 600 kPa. The achieved thickening of cooling water was N=4. Side filtering was accomplished by a filter DPF 4000. The pipes of the cooling circuit were welded to each other, which initiated stress stimulating development of cracks on the outer surface of pipes in the heat-affected zone, Fig.1. The existing technological conditions resulted in formation of deposits on the outer pipe surfaces. Their presence changed thermal conditions in steel pipes.

Corrosion of boiler tubes remains an operational and economic limitation in municipal waste power plants. The understanding of the nature, mechanism, and related factors can help reduce the degradation process caused by corrosion. The chlorine content in the fuel has a significant effect on the production of gaseous components (e.g., HCl) and condensed phases on the chloride base. This study aimed to analyze the effects of flue gases on the outer surface and saturated steam on the inner surface of the evaporator tube. The influence of gaseous chlorides and sulfates or their deposits on the course and intensity of corrosion was observed. The salt melts reacted with the steel surface facing the flue gas flow and increased the thickness of the oxide layer up to a maximum of 30 mm. On the surface not facing the flue gas flow, they disrupted the corrosive layer, reduced its adhesion, and exposed the metal surface. Beneath the massive deposits, a local overheating of the inner surface of the evaporator tubes occurred, which resulted in the release of the protective magnetite layer from the surface. Ash deposits reduce the boiler’s thermal efficiency because they act as a thermal resistor for heat transfer between the flue gases and the working medium in the pipes. The effect of insufficient feedwater treatment was evinced in the presence of mineral salts in the corrosion layer on the inner surface of the tube.

Nowadays, more and more scientific studies deal with the formation of electroplating alloy coatings due to the possibility of combination and share content type metal – forming alloy. To produce coatings that fulfil pre-defined specific requirements is possible by a suitable combination of process conditions. The paper deals with the study of tribological properties of Ni-Co coatings that were prepared by electrodeposition technique from sulphate electrolyte on the copper substrate. Effect of current density on the properties of electroplated coatings was determined via a morphology characteristics and micro-hardness of coating′surface. The tribological behaviour of Ni – Co coatings was described by friction coefficient using the pin-on-disc method.

Welding of different types of steel is fundamental proces for the production of car bodies. Fatigue degradation is still a significant factor in long-term use. Current trends welding and combinations of different types of steel are used. The specific form of the course of fatigue in the welded joints is followed. Test samples loaded fatigue tests, microscopic and scanning electron microscopy analysis of welded joints of steel type IF (DC06EK) and DP (DP600MC) are done. The resulting values of endurance tests are graphically processed by the Wöhler curve.

Four hard thin coatings (TiSiN, TiN-CrN multi, AlTiN a WC) were deposited on the WC+Co substrate by cathodic arc deposition. Adhesion test of PVD coatings was evaluated by comparison failure of coating surfaces. The surface features after the Rockwell indentation test were examined by light microscopy. The results showed that the AlTiN and WC coatings exhibited acceptable failure and are appropriate for usage in practice. Unlike them, had TiSiN and TiN-CrN coatings poor adhesion, which resulted in unacceptable failure after Rockwell C test.