TY - JOUR
T1 - Corrosion rate of construction materials in hot phosphoric acid with the contribution of anodic polarization
AU - Kouril, M.
AU - Christensen, Erik
AU - Eriksen, S.
AU - Gillesberg, B.
PY - 2011
Y1 - 2011
N2 - The paper is focused on selection of a proper material for construction elements
of water electrolysers, which make use of a 85% phosphoric acid as an
electrolyte at temperature of 150 8C and which might be loaded with anodic
polarization up to 2.5 V versus a saturated Ag/AgCl electrode (SSCE). Several
grades of stainless steels were tested as well as tantalum, niobium, titanium,
nickel alloys and silicon carbide. The corrosion rate was evaluated by means of
mass loss at free corrosion potential as well as under various levels of
polarization. The only corrosion resistant material in 85% phosphoric acid at
150 8C and at polarization of 2.5 V/SSCE is tantalum. In that case, even a gentle
cathodic polarization is harmful in such an acidic environment. Hydrogen
reduction leads to tantalum hydride formation, to loss of mechanical properties
and to complete disintegration of the metal. Contrary to tantalum, titanium is
free of any corrosion resistance in hot phosphoric acid. Its corrosion rate ranges
from tens of millimetres to metres per year depending on temperature of the
acid. Alloy bonded tantalum coating was recognized as an effective corrosion
protection for both titanium and stainless steel. Its serviceability might be
limited by slow dissolution of tantalum that is in order of units of mm/year.
AB - The paper is focused on selection of a proper material for construction elements
of water electrolysers, which make use of a 85% phosphoric acid as an
electrolyte at temperature of 150 8C and which might be loaded with anodic
polarization up to 2.5 V versus a saturated Ag/AgCl electrode (SSCE). Several
grades of stainless steels were tested as well as tantalum, niobium, titanium,
nickel alloys and silicon carbide. The corrosion rate was evaluated by means of
mass loss at free corrosion potential as well as under various levels of
polarization. The only corrosion resistant material in 85% phosphoric acid at
150 8C and at polarization of 2.5 V/SSCE is tantalum. In that case, even a gentle
cathodic polarization is harmful in such an acidic environment. Hydrogen
reduction leads to tantalum hydride formation, to loss of mechanical properties
and to complete disintegration of the metal. Contrary to tantalum, titanium is
free of any corrosion resistance in hot phosphoric acid. Its corrosion rate ranges
from tens of millimetres to metres per year depending on temperature of the
acid. Alloy bonded tantalum coating was recognized as an effective corrosion
protection for both titanium and stainless steel. Its serviceability might be
limited by slow dissolution of tantalum that is in order of units of mm/year.
U2 - 10.1002/maco.201006021
DO - 10.1002/maco.201006021
M3 - Journal article
SN - 0947-5117
VL - 62
JO - Materials and Corrosion
JF - Materials and Corrosion
IS - 9999
ER -