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Hello everyone. My name is Sam Chrun I'm a project engineer here at Blue Oak Energy,
and I'd like to welcome you to another episode of Tech Talk Tuesday. Today we'll be discussing
corrosion of steel piles on ground mounted PV systems. So what is corrosion? Corrosion
is typically defined as a gradual destruction of materials due to a chemical reaction with
its environment. Steel piles are typically subjected to two different types of corrosions:
atmospheric corrosion and soil corrosion. Atmospheric corrosion occurs on the portion
of the pile that is above grade, and soil corrosion occurs on the portion of the pile
that's below grade. If piles are driven into near neutral soils, the major factor that
controls corrosion rate is the soil electrical resistivity, which is defined as the soil's
resistance to electrical current across a cubic meter of earth, which is typically driven
by soil chemical properties and also the amount of moisture within the soil. As you can see
on the table to my left here, resistivity is measured in ohms-cm, and as you can see
at the top of the table there, resistivity values between 0 and 500 would deem the soil
to be severely corrosive. However, as you get higher in the resistivity values, the
soil tends to be less corrosive. As you can see, anything above 32,000 the soil is deemed
to be progressively less corrosive. However, if the piles are to be coated or galvanized
with zinc, pH also plays a major role in corrosion rates, as extremely low pH level tends to
accelerate the corrosion of the zinc plating. As you can see there. in my table here, anything
less than six, the corrosion classification for that particular pH level is severely corrosive.
As you approach near neutral soils, which is above seven, you get mildly corrosive conditions
to the steel piles. Soil sulfate and soil chloride also play a role in corrosion rates,
however, to a much lesser extent than electrical resistivity and pH level. For the next Tech
Talk, we'll like to get into further detail on methods to mitigate soil corrosion. But
for now, I hoped you've learned something from this Tech Talk, and we'll see you next
time. Thanks.