Search

Purpose – The purpose of this paper is to synthesize anticorrosion pigments of the perovskite type, YXO3, where X = Ti, Zr, Mn or Al and Y = Ca, Sr, La or Fe, for coating materials intended for corrosion protection of metals. Also, to synthesize pigments containing hexavalent Mo and W (double perovskites). Design/methodology/approach – The anticorrosion pigments were synthesized from oxides or carbonates by a high-temperature process. The following pigments were synthesized: CaTiO3, SrTiO3, CaZrO3, SrZrO3, LaTiO3, LaMnO3, CaMnO3, SrMnO3, LaFe2O3, SrFe2O3, LaAlO3, Ca2ZnWO6 and Ca2ZnMoO6. The pigments were characterized by the physico-chemical properties of the powders, by X-ray diffraction analysis and by scanning electron microscopy. Epoxy-ester coating materials containing the pigments at a volume concentration PVC = 10 per cent were prepared and subjected to tests examining their physico-mechanical properties and tests in simulated corrosion atmospheres. Findings – The perovskite structure was identified in the majority of the pigments. The pigments were found to impart good corrosion inhibiting properties to coating materials. The highest calculated anticorrosion efficiency was found for paints containing CaMnO3 or SrMnO3 as the pigments. Practical implications – The pigments synthesized can be used with advantage in paints intended for corrosion protection of the substrate metals. Originality/value – The use of the above pigments in anticorrosion coating materials to protect metals is new. Especially beneficial are the uses and procedures for the synthesis of anticorrosion pigments which do not contain heavy metals and are acceptable from the environmental protection aspect.

Purpose - The purpose of this paper is to verify the capability of pigmented coatings to mitigate the effects of thermal sensitisation of 430 stainless steel. Design/methodology/approach - Experimental weld joints of non-stabilised ferritic corrosion resistant steel type AISI 430 were prepared. Protective coatings in several variants were applied to a number of weldments, subsequently subject to corrosion tests in SO2 and NaCl. The anticorrosive efficiency of the coatings was evaluated by means of normative visual assessment and metallographic analysis of the mechanism and depth of corrosion damage. Findings - Anticorrosive efficiency of the tested coatings was experimentally established under conditions where differences were identified in structural changes caused by welding, or resulting from mechanical damage to the coating. Differences in the progress of corrosion damage caused by phase changes in the heat-affected zone were established. Practical implications - Tests of anticorrosive efficiency of coatings of selected types provided information about possible reduction in sensitisation of welded non-stabilised steel. The effect of the investigated processes on degradation of anticorrosive resistance was identified. Originality/value - A specific effect of phase changes accompanying welding on the corrosion mechanism was described and so were the reasons underlying development of corrosion damage at visually identical character of surface damage. Anglická klíčová slova: stainless steel; coatings; pigments; corrosion; destabilisation; welding; corrosion resistant ferritic steels; anticorrosive pigment; zinc; organic coating Práce se zabývá možnostmi zvýšení korozní odolnosti svařovaných korozivzdorných ocelí. V místě sváru a jeho okolí dochází ke zcitlivění materiálu na korozní působení. V práci jsou testovány možnosti zvýšení korozní odolnosti na těchto senzibilizovaných materiálech po povlakování pigmenovanými nátěry s různým složením.

PurposeThe purpose of this paper is to clarify the destabilisation mechanism that occurs with two types of ferritic corrosion‐resistant steel during the welding cycle.Design/methodology/approachA series of experimental weld joints was made to verify the actual response of non‐stabilised corrosion‐resistant steel, and of the same steel that had been stabilised by added titanium. The character and extent of the ensuing structural changes were analysed. The essential characteristics of degradation in the heat‐affected zone are evaluated using optical and scanning electron microscopy; individual phases are identified by means of EDX microanalysis. The underlying mechanism for the loss of stability is induced experimentally in several stages; depending on the thermal doping level and interaction with the environment during the welding process, phases of various types are precipitated. These phases subsequently are studied in connection with the original microstructural characteristics of the steel and the induced grain boundary decohesion of the surface layer. The scope and character of the damage are analysed and the results verified by analysing the actual operating damage to the weldment.FindingsA degradation mechanism of stabilised corrosion‐resistant steel 1.4510 is induced that is associated with destabilisation of titanium phases. The importance is demonstrated of ensuring that a protective atmosphere is maintained during welding, and various phase changes in the surface layers are identified that can delimit the use of appropriate post‐weld passivation procedures.Practical implicationsIdentification of the mechanism underlying the damage to the surface layer in welded stabilised ferritic steel will find application in development of welding technology, specifically in designing a technology process and subsequent surface treatment.Originality/valueThe results bring new knowledge of material response of steel 1.4510 under specific material processing conditions; a destabilisation mechanism related to precipitation of several titanium‐containing phases is identified. The result enables the fatigue limit of the welded material as a function of the welding technology employed, which offers increased service life under specific application conditions.