CFESA Steam Study Guide Chapter 5 -
Corrosion
1.Describe the principal of galvanic cell corrosion? - answera. Galvanic corrosion is the
corrosion or decay of the metal created when different metals are in the same liquid
solution.
2.Galvanic corrosion has two corrosion poles, what are they called? - answera. Anode
and cathode
3.The pole that corrodes away is referred to as the? - answera. anode
4.The pole where the corrosion residue builds up is called the? - answera. cathode
5.Why is zinc such a good metal to use for an anode? - answera. Because it is a low on
the galvanic chart. Whenever two metals are in the same solution, the metal that is
lower on the chart will always corrode away.
6.Describe the difference between active and passive stainless steel. - answera. Active
stainless steel is more subject to corrosion because it is stainless steel that is cut off
from oxygen. Passive stainless steel is open to oxygen and resistive to corrosion.
7.Give some examples of conditions that can make stainless steel active. - answera.
Stainless steel can become active when it is covered in scale, or when the surface has
a deep scratch on it.
8.Which will corrode away first, active or passive stainless steel? - answera. Active
9.If steel and brass pipe fittings are mixed, which will corrode away? - answera. Steel,
because it is lower on the galvanic chart
10.What is the purpose of a corrosion resistor corrodes used in a boiler? - answera. It is
an anode because it is lower on the galvanic chart than any of the other metals in the
boiler. Therefore, it will corrode away before any of the boiler steel.
11.What happens if the corrosion resistor corrodes away completely? - answera. The
corrosion starts on the boiler shell
12.In order for a corrosion resistor to do its job properly, how must it be installed -
answera. It must be tightly attached to a clean metal surface connected to the boiler
shell such as a steel strut in the boiler shell
Corrosion
1.Describe the principal of galvanic cell corrosion? - answera. Galvanic corrosion is the
corrosion or decay of the metal created when different metals are in the same liquid
solution.
2.Galvanic corrosion has two corrosion poles, what are they called? - answera. Anode
and cathode
3.The pole that corrodes away is referred to as the? - answera. anode
4.The pole where the corrosion residue builds up is called the? - answera. cathode
5.Why is zinc such a good metal to use for an anode? - answera. Because it is a low on
the galvanic chart. Whenever two metals are in the same solution, the metal that is
lower on the chart will always corrode away.
6.Describe the difference between active and passive stainless steel. - answera. Active
stainless steel is more subject to corrosion because it is stainless steel that is cut off
from oxygen. Passive stainless steel is open to oxygen and resistive to corrosion.
7.Give some examples of conditions that can make stainless steel active. - answera.
Stainless steel can become active when it is covered in scale, or when the surface has
a deep scratch on it.
8.Which will corrode away first, active or passive stainless steel? - answera. Active
9.If steel and brass pipe fittings are mixed, which will corrode away? - answera. Steel,
because it is lower on the galvanic chart
10.What is the purpose of a corrosion resistor corrodes used in a boiler? - answera. It is
an anode because it is lower on the galvanic chart than any of the other metals in the
boiler. Therefore, it will corrode away before any of the boiler steel.
11.What happens if the corrosion resistor corrodes away completely? - answera. The
corrosion starts on the boiler shell
12.In order for a corrosion resistor to do its job properly, how must it be installed -
answera. It must be tightly attached to a clean metal surface connected to the boiler
shell such as a steel strut in the boiler shell
