3
pH is thought to be because of the presence of shotcrete in
effect neutralizing the acids and precipitating salts.
A summary of the work to date substantiates that:
• Extremely corrosive aqueous conditions are present
in the existing development.
• Ventilation enhances oxygen diffusion into the dam-
aged wall rock(near surface)
• Near surface pyrite oxidation is occurring, and sec-
ondary mineral precipitation including acidic efflo-
rescent sulfate minerals.
• Groundwater monitoring at depth in intact rock
shows a low presence of O2 to the deep saturated zone
in isolated rock masses, and low-pH/acidic condi-
tions should not be expected for most of the embed-
ded bolts and intact rock mass. The acids produced
are most likely confined to the first 1–1.5 meters into
the rock.
• Susceptibility to water inflows, oxidation and sub-
sequent corrosion from acid are influenced by blast
damage or increased loosening between the shotcrete
shell and the intact rock mass.
• Most of the mineralized subsurface is expected to
be net acid generating once exposed by mining and
ventilation. For these ventilated areas, wall rock and
associated local seepage pH 4 should be common
after a few months to years of exposing pyrite-bear-
ing rock to atmospheric oxygen. High oxidation
potential will be present everywhere in the ventilated
zones.
Nature and Causes of Corrosion
The two main types of corrosion are classified as aqueous
(interstitial mine water), and from high humidity (60%),
and lesser amounts from stress corrosion cracking associ-
ated with very low PH 2 for higher strength steels. Table 3
concentrates on the two main categories of corrosion and
accepted mitigation of corrosion. Figure 3 is summary of
classifications of aqueous corrosion based on pH and TDS
(total dissolved solids). Corrosion is also therefore highly
dependent on dissolved oxygen. Figure 4 shows that atmo-
spheric corrosion (humidity) can be even more pervasive
in stagnant versus moving exhaust or mixed air due to the
concentrations of SO2 vapors.
Corrosion from Electrolysis
The electrochemical corrosion involves the flow of elec-
trons (+)and ions (–), and involves an anode, cathode and
electrolyte. Reaction at the anode is oxidation where elec-
trons are generated, where metal atoms go into solution
and the metal gets thinner. The anode is the site where the
Figure 2. Plan map of TPL2(68 level) showing total percent
sulfur from geology block model
Figure 3. Classification of aqueous corrosion and estimated
corrosion rates for salinities, dissolved oxygen, or total
dissolved solids. From Preston and others, 2019
Table 3. The types of corrosions and their effects and
strategery priorities
pH is thought to be because of the presence of shotcrete in
effect neutralizing the acids and precipitating salts.
A summary of the work to date substantiates that:
• Extremely corrosive aqueous conditions are present
in the existing development.
• Ventilation enhances oxygen diffusion into the dam-
aged wall rock(near surface)
• Near surface pyrite oxidation is occurring, and sec-
ondary mineral precipitation including acidic efflo-
rescent sulfate minerals.
• Groundwater monitoring at depth in intact rock
shows a low presence of O2 to the deep saturated zone
in isolated rock masses, and low-pH/acidic condi-
tions should not be expected for most of the embed-
ded bolts and intact rock mass. The acids produced
are most likely confined to the first 1–1.5 meters into
the rock.
• Susceptibility to water inflows, oxidation and sub-
sequent corrosion from acid are influenced by blast
damage or increased loosening between the shotcrete
shell and the intact rock mass.
• Most of the mineralized subsurface is expected to
be net acid generating once exposed by mining and
ventilation. For these ventilated areas, wall rock and
associated local seepage pH 4 should be common
after a few months to years of exposing pyrite-bear-
ing rock to atmospheric oxygen. High oxidation
potential will be present everywhere in the ventilated
zones.
Nature and Causes of Corrosion
The two main types of corrosion are classified as aqueous
(interstitial mine water), and from high humidity (60%),
and lesser amounts from stress corrosion cracking associ-
ated with very low PH 2 for higher strength steels. Table 3
concentrates on the two main categories of corrosion and
accepted mitigation of corrosion. Figure 3 is summary of
classifications of aqueous corrosion based on pH and TDS
(total dissolved solids). Corrosion is also therefore highly
dependent on dissolved oxygen. Figure 4 shows that atmo-
spheric corrosion (humidity) can be even more pervasive
in stagnant versus moving exhaust or mixed air due to the
concentrations of SO2 vapors.
Corrosion from Electrolysis
The electrochemical corrosion involves the flow of elec-
trons (+)and ions (–), and involves an anode, cathode and
electrolyte. Reaction at the anode is oxidation where elec-
trons are generated, where metal atoms go into solution
and the metal gets thinner. The anode is the site where the
Figure 2. Plan map of TPL2(68 level) showing total percent
sulfur from geology block model
Figure 3. Classification of aqueous corrosion and estimated
corrosion rates for salinities, dissolved oxygen, or total
dissolved solids. From Preston and others, 2019
Table 3. The types of corrosions and their effects and
strategery priorities