4
metal is corroded the electrolyte solution is the corrosive
mechanism with the cathode forming the other electrode.
At the cathode, reductions take place consuming electrons.
Increasing salinity and higher temperatures of the electro-
lyte promote the corrosion effects.
Aqueous Corrosion by Acidic Formation
Logsdon (2022) summarized the underlying geochemical
reactions are summarized when pyrite (FeS2) is exposed to
oxygen (O2) and water (H2O), the sulfur and then the iron
in the pyrite will oxidize, dissolved ferric ion (Fe3+) will
hydrolyze (react with hydroxyl ions, OH–), precipitating
secondary ferric minerals, and release yet addition H+.
The long-term consequence is acidic, low-pH, and
high Total Dissolved Solids (TDS) waters, plus conversion
of reduced iron (Fe2+) to oxidized iron (Fe3+), i.e., corro-
sion. The classical conceptual reaction series is:
FeS2 +7/2O2 +H2O → Fe2++ 2 SO42– +2 H+
Fe2+ 1/4O2 +H → Fe3+ +1/2H2O
Fe3+ +3 H2O → Fe(OH)3 +3 H+
Total: FeS2 +15/4 O2 +7/2 H2O → Fe(OH)3 +2
SO42– +4 H
Corrosion Precipitates
In systems that evolve to very low pH (pH 2) highly hydrated
ferric sulfates such as copiapite [Fe2+Fe3+4[SO4]6(OH)2
.20H20]) form the sorts of efflorescent precipitates.
Figures 4–6 show low pH paste and efflorescent salts effeec-
tion bolt corrosion.
BOLTS TESTING-METALLURGY RESULTS
Bolt testing has been done at the 68 level workings which
summarize the service life of the bolts installed in similar
Figure 4: Examples of corrosion precipitates in cracks
through shotcrete
Figure 5: Examples of corrosion precipitates from
TPL2(68L) indicates hydroxysulfates such as jarosite [KFe
(SO )(OH) ].From Logston, 2022
Figure 6 Corroded rock bolt extracted from 68 Level .Note
corrosion although portion of the bolt was surrounded by
shotcrete. Yellow (white to greenish) efflorescent minerals are
recent/current precipitates
metal is corroded the electrolyte solution is the corrosive
mechanism with the cathode forming the other electrode.
At the cathode, reductions take place consuming electrons.
Increasing salinity and higher temperatures of the electro-
lyte promote the corrosion effects.
Aqueous Corrosion by Acidic Formation
Logsdon (2022) summarized the underlying geochemical
reactions are summarized when pyrite (FeS2) is exposed to
oxygen (O2) and water (H2O), the sulfur and then the iron
in the pyrite will oxidize, dissolved ferric ion (Fe3+) will
hydrolyze (react with hydroxyl ions, OH–), precipitating
secondary ferric minerals, and release yet addition H+.
The long-term consequence is acidic, low-pH, and
high Total Dissolved Solids (TDS) waters, plus conversion
of reduced iron (Fe2+) to oxidized iron (Fe3+), i.e., corro-
sion. The classical conceptual reaction series is:
FeS2 +7/2O2 +H2O → Fe2++ 2 SO42– +2 H+
Fe2+ 1/4O2 +H → Fe3+ +1/2H2O
Fe3+ +3 H2O → Fe(OH)3 +3 H+
Total: FeS2 +15/4 O2 +7/2 H2O → Fe(OH)3 +2
SO42– +4 H
Corrosion Precipitates
In systems that evolve to very low pH (pH 2) highly hydrated
ferric sulfates such as copiapite [Fe2+Fe3+4[SO4]6(OH)2
.20H20]) form the sorts of efflorescent precipitates.
Figures 4–6 show low pH paste and efflorescent salts effeec-
tion bolt corrosion.
BOLTS TESTING-METALLURGY RESULTS
Bolt testing has been done at the 68 level workings which
summarize the service life of the bolts installed in similar
Figure 4: Examples of corrosion precipitates in cracks
through shotcrete
Figure 5: Examples of corrosion precipitates from
TPL2(68L) indicates hydroxysulfates such as jarosite [KFe
(SO )(OH) ].From Logston, 2022
Figure 6 Corroded rock bolt extracted from 68 Level .Note
corrosion although portion of the bolt was surrounded by
shotcrete. Yellow (white to greenish) efflorescent minerals are
recent/current precipitates