Árbók VFÍ/TFÍ - 01.06.1998, Page 306

4.3
Ragnheiður Inga Þórarinsdóttir, Iðntæknistofnun íslands
Einar Þorsteinsson, Rannsóknastofnun byggingariðnaðarins
Tæring lóðmálma
í súlfíðríku hitaveituvatni
Abstract
This paper describes the corrosion observed in
three test rigs of copper pipes joined with eight
different brazing alloys. The test rigs have been ex-
posed to district heating water at different places in
Reykjavik for 12 months. The brazing alloys in-
vestigated were the copper-phosphorus brazing all-
oys, L-CuP6, L-Ag2P, L-Ag5P and L-AgI5P, the
silver brazing alloys, L-Ag40Cd and L-Ag40Sn
and the soft solders S-SnAg3 and S-SnCu3.
The water is of geothermal origin at two test
locations with different chemical composition,
and quite unlike the third place which is heated
fresh water, where steam containing sulphide has
been added.
The corrosion attack on copper duc to sul-
phide is relatively even, resulting in black copper
sulphide scaling. The attack is more distinctive in
the heated fresh water with added suiphide com-
pared to the geothermal water. The scaling is
more porous in the heated fresh water with a
thickness of 0,2-0,3 mm compared with more
dense copper sulphide scaling of 0,02-0,05 mm
thickness in the geothermal water.
The copper-phosphorus brazing alloys are evenly corroded in the geolhermal water. At some joints
metallic copper and silver are observed on the surfaces. In the heated fresh water, a more severe attack
takes place with selective corrosion of the copper phases in the brazing metal and simultaneous cor-
rosion of the parent copper metal of the adjoining surfaces. The corrosion attack measured is up to 2
mm deep and voluminous quantity of copper sulphide is observed as corrosion product.
The corrosion attack on the silver brazing alloy, L-Ag40Sn, is significant in all three test rigs. The
copper dendrites are selectively corroded together with the adjoining surfaces of the copper pipes,
which are corroded about 1 mm. The L-Ag40Cd joints on the other hand showed no corrosion.
The soft solders, S-SnAg3 and S-SnCu3, showed no or very little corrosion (<0,12 mm) in the
three test rigs.
Ragnheiður Inga Þórarinsdóttir hefur
starfað á Iðntæknistofnun íslands frá
1994. Hún útskrifaðist
sem efnaverkfræð-
ingur með civ. ing.
próf frá DTH í Dan-
mörku 1993 og
stundar nú Ph.D. nám
við DTU.
Einar Þorsteinsson byggingatæknifræð-
ingur hefur starfað
sem deildarstjóri
lagnadeildar Rann-
sóknastofnunar
byggingariðnaðarins
frá 1991. Hann út-
skrifaðist frá Tækni-
skóla íslands 1976.