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Author:Leppänen, Hanna
Title:Eräiden kupariseosten korroosionkesto muurahaishappoliuoksissa
Corrosion of some copper alloys in formic acid solutions
Publication type:Master's thesis
Publication year:2005
Pages:66+9      Language:   fin
Department/School:Materiaalitekniikan osasto
Main subject:Korroosionestotekniikka   (Mak-85)
Supervisor:Forsen, Olof
Instructor:Pehkonen, Antero ; Korpinen, Tapio
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark V80     | Archive
Abstract (eng): The purpose of this thesis was to find the best corrosion resistant copper alloy for copper tubes, which are used in heat-exchanging, refrigerating and air-.conditioning units.
In theoretical section of the thesis corrosion mechanism, in-Influencing factors, history and cases of formicary corrosion were studied.
In same context also widely used method in reproduction test and different preventive measures based on literature survey were presented.
In addition of this, I corrosion of aluminium and zinc in formic acid solution were also studied.

In experimental part of the thesis the corrosion behaviour of pure copper, aluminium, tin, zinc and some copper alloys were studied in formic acid solutions.
The behaviour of pure copper was also studied in sulphuric acid solutions.
Linear polarization resistance, anodic and cathodic polarization and impedance measurements were used as research methods.
Several electrolytic solutions were used in the investigation.
In preliminary study the effect of three different formic acid solutions on pure copper was investigated.

Based on this preliminary study aqueous solution containing 5 vol % formic acid was chosen and in that solution all the other materials were studied.
Due to comparison the effect of pure copper was studied in two sulphuric acid solutions, which had the same pH-values as equivalent formic acid solutions.
Different materials were also studied in formic acid solution whose pH-value was raised and in a solution where copper ions had added to that.
In addition test similar to the reproduction test, was carried out on the copper tubes.
The purpose of that test was to repeat the test and compare the results with results of other researchers.

Based on tests it was concluded that pure aluminium was the least corroding metal in test conditions.
However, no big differences were found in the behaviour of the different copper alloys.
Copper alloy no. 12 and Nordic gold were least corroding metals in the group of copper alloys.
Formicary corrosion was not noticed in reproduction test.
If there were formicary corrosion on copper tubes it was very difficult to find.
Based on test formicary corrosion does not seem to be an own corrosion.
Abstract (fin): Työn päämääränä oli löytää korroosion keston kannalta paras kupariseos lämmönvaihtimissa, ilmanvaihto- ja jäähdytyslaitteissa käytettäviin kupariputkiin.
Kirjallisuusosassa tarkasteltiin muurahaiskekokorroosion historiaa, korroosiotapauksia, korroosiomekanismia ja korroosioon vaikuttavia tekijöitä.
Samassa yhteydessä esiteltiin myös simulointikokeissa yleisesti käytetty menetelmä ja erilaisia kirjallisuudesta löytyviä korroosiota estäviä toimenpiteitä.
Tämän lisäksi tarkasteltiin alumiinin ja sinkin korroosiota muurahaishapossa.

Kokeellisessa osassa tutkittiin puhtaan kuparin, alumiinin, tinan ja sinkin sekä eräiden kupariseosten käyttäytymistä muurahaishappoliuoksissa.
Puhtaan kuparin käyttäytymistä tutkittiin lisäksi rikkihappoliuoksissa.
Tutkimusmenetelminä käytettiin vastuspolarisaatiomittausta, anodista ja katodista polarisaatiomittausta ja impedanssimittausta.
Tutkittavia elektrolyyttiliuoksia oli useita.

Esitutkimuksessa tutkittiin kolmen eri vahvuisen muurahaishappoliuoksen vaikutuksia puhtaaseen kupariin ja tämän perusteella valittiin tutkittavaksi muurahaishappoliuokseksi 5 til- % -liuos, jossa kokeet muille materiaaleille tehtiin.
Vertailun vuoksi puhtaan kuparin käyttäytymistä tutkittiin myös kahdessa rikkihappoliuoksessa, joiden pH-arvot olivat samat kuin vastaavien muurahaishappoliuosten.

Eri materiaaleja tutkittiin my6s muurahaishappoliuoksessa, jonka pH-arvoa oli nostettu ja vastaavassa liuoksessa, johon oli lisätty kupari-ioneja.
Kokeellisessa osassa tehtiin my6s simulointikokeen mukainen koe kupariputkille.
Tehdyn kokeen tarkoituksena oli toistaa ja vertailla saatuja tuloksia muiden tutkijoiden vastaaviin tuloksiin.

Kokeiden perusteella havaittiin, että puhdas alumiini kestää koeolosuhteissa parhaiten.
Sen sijaan eri kupariseosten käyttäytymisessä ei havaittu suuria eroja.
Kupariseoksista parhaiten kestivät kupariseos nro 12 ja Nordia gold.
Simulointikokeissa ei varmuudella löydetty muurahaiskekokorroosiota.
Jos kupariputkissa esiintyikin muurahaiskekokorroosiota, oli sitä hyvin vaikea löytää.
ED:2006-04-11
INSSI record number: 31501
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