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Material parameters affecting degradation processes of Al-brasses in pipe systems

Liptáková T., Lovíšek M., Hadzima B., Dundeková S.

Archives of Materials Science and Engineering

2015

Vol. 76, nr 1

27--34

Purpose: As construction material of cooling pipe systems there are often used Al-brasses because their high thermal conductivity, mechanical workability and corrosion resistance. In the pipes liquid media of various chemical compositions are flowing by different rates. It means that the material is loaded mechanically also chemically what results in synergy effect on degradation. Susceptibility to corrosion-erosion damage of four Al-brasses manufactured by different producers is investigated because in operation conditions they have different reliability and lifetime. Design/methodology/approach: By studying of their microstructure, surface state, selected mechanical properties and corrosion characteristics the parameters which affected chemicalmechanical degradation were evaluated. Experimental methods are SEM, EDX and spectral analyses, measurement of microhardness and roughness. Findings: By actual obtained results it was identified that in spite of very similar chemical composition differences in mechanical and corrosion behaviour are affected by technology of manufacturing. It can explain their different durability in operating conditions. Research limitations/implications: To identify more precisely the main parameters important for degradation resistance in various flow media the original experimental device is designed and constructed. The device makes possible to test Al-brasses in various flowing media by the same mail at three flowing rates. By long time lasted experiments in the one it is able to simulated operation specification. Results of the device are not presented yet because they are just in progress. Practical implications: Obtained results will be very helpful for choice of Al-brasses for required operation conditions according important properties which were experimentally verified. Originality/value: It means contribution to economy by material saving in operation by available choice and design and construction of original experimental device.

Uszkodzenia erozyjno-korozyjne elementów w obiegu wody zasilającej

Zbroińska-Szczechura E.

Energetyka

2008

nr 12

846-850

Ścianki elementów pracujących w obiegu wody zasilającej, od powierzchni zewnętrznej i wewnętrznej, ulegają uszkodzeniom pod wpływem erozjo-korozji. Proces polega na mechanicznym i chemicznym niszczeniu warstwy ochronnej, okresowo powstającej na powierzchniach kontaktujących się z wodą zasilającą, a przyczyną bezpośrednią jest rozpuszczanie warstwy ochronnej wskutek niskiego pH i zawartości związków chemicznych o dużym powinowactwie do tlenu oraz usuwania jej strumieniem wody. W literaturze proces określony jest jako korozja podczas przepływu czynnika (Flow Assisted Corrosion-FAC). Opisano charakter uszkodzenia, miejsca występowania oraz sposoby zapobiegania.

The walls of elements operated in the feed water circulation system are subjected to damage on their internal and external surfaces due to erosion-corrosion. The above process consists in that the protective layers periodically formed on the surfaces in contact with feed water are mechanically and chemically destroyed whereas the direct cause lies in the protective layer being dissolved due to a low pH value and chemical compounds with high affinity to oxygen followed by its removal with a jet of water. In the professional literature this process is called: Flow Assisted Corrosion (FAC). This paper describes the nature of the damage, its location as well as preventive methods.