Pitting corrosion of stainless steel welded joints

Visokolegirani korozijski postojani Cr-Ni celici nalaze svoju sve siru primjenu u brojnim industrijskim podrucjima, arhitekturi i gradjevinarstvu, medicini i dr., a jedno od znacajnijih podrucja njihove primjene je i izrada razlicitih zavarenih konstrukcija izloyenih morskom okolisu npr. u brodogradnji, off shore tehnici i sl.. Iako se ovi materijali zavaruju bez znacajnijih poteskoca ukoliko se uvazavaju njihove specificnosti poput npr. izrayene sklonosti deformacijama, kao posljedica unosa topline tijekom zavarivanja moze doci do znatnog smanjenja svojstava korozijske otpornosti sto u okolisu kakav je more i morska atmosfera moze dovesti do intenzivnih lokalnih korozijskih ostecenja u podrucjima zavarenih spojeva – zonama strukturnih i povrsinskih nehomogenosti. U radu su prikazana osnovna svojstva pojedinih skupina Cr-Ni celika, posebnosti kada je u pitanju njihovo zavarivanje te su dani primjeri korozijskih ostecenja u podrucjima zavarenih spojeva uz prikaz mogucnosti njihovog izbjegavanja. Detaljnije je obradjena rupicasta korozija te je provedeno eksperimentalno ispitivanje prema normi ATM G 48 s ciljem utvrdjivanja korozijske otpornosti razlicitih vrsta austenitnih nehrdj0ajucih celika i utjecaja toplinskih oksida i naknadne kemijske obrade zavara.Cr - Ni alloyed stainless steels are very corrosion resistant and are regularly used in industry, architecture, civil engineering, medicine, but are also among the most used metals for welded joint structures which are used in maritime conditions, such as salty water. Although stainless steel can be welded without any problem, we have to consider that the heat input by welding can change the steel properties and reduce the corrosion resistance, which can be very harmful in aggressive conditions, such as salty sea water. These can lead to serious corrosion of welded joints which are the least resistant because of inhomogeneities in microstructure and on the surface. The basic properties of groups of Cr-Ni steels are presented in work, especially when it comes to their welding, and examples of corrosion damage in the welded joints are given, with the possibilities of avoiding them. Pitting corrosion was treated in more detail and experimental testing was performed according to ASTM G 48 standard in order to test corrosion resistance of different types of austenitic steel and the effect of heat tints oxides and chemical post weld treatment were investigated