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result in savings of 70% in time and money. In addition, replacing the anodes of the
water provides protection from sudden floods, which can result in indirect costs for
clean-ups and damages. The indirect cost can potentially be greater than costs related
to installing a new tank or retrofitting an old tank. The life expectancy of sacrificial
anodes can range from 2 to 3 years to more than 10 years. The benefits of anode
maintenance are (i) long-lasting tanks; (ii) less rust buildup; (iii) saving on costly
changeovers.
The cost of replacing water heaters was estimated at $460 million/year, the cost of
anode replacement was estimated at $780 million per year, and the cost of increased
life expectancy of water heaters was estimated at $778 million/year.
The benefits of anode maintenance are longer tank life, less rust buildup, and sav-
ings on costly changeovers. However, a cost–benefit analysis may show the cost of
replacing anodes could exceed the cost of increased life expectancy or the cost of
water heater replacement. Increased life expectancy without increased cost has not
been shown to be technically feasible. It is also not known how much life is gained by
the replacement of water heater anodes as the water heater can fail because of other
reasons such as heating element failure.

4.33.2 Corrosion Control by Corrosion-Resistant Materials
Whenever possible, carbon steel may be used because of its high strength and low
cost. However, corrosion-resistant materials such as plastics, galvanized steel, stain-
less steels, aluminum, and copper–nickel alloys are used in corrosive environments.
Plastics are corrosion resistant and they prolong the product life and durability in
hostile environments where major appliances operate. The use of plastics increases
the durability and equipment life by 30–40%.
Carbon steel coated with zinc is known as galvanized steel, which protects the
cold-rolled steel from corrosion in aqueous and high-temperature environments. Gal-
vanized steel is used in laundry appliances as it provides resistance to laundry deter-
gents. The cost of converting steel into the galvanized condition depends on the
facility, but ranges between $50 and $100/metric ton of zinc.
Stainless steels are usually used to design high-efficiency furnace components
such as heat exchangers. According to the Specialty Steel Industry of North Amer-
ica the total steel usage for heating and air-conditioning equipment is 81 million kg,
and the annual (1998) consumption of stainless steel for the appliance sector was esti-
mated at $315 million/year. This estimate can be attributed to the control of corrosion
by using stainless steels.
Aluminum is often used for control panels of appliances. The thin film of alu-
minum oxide that forms readily on exposure to air gives protection against corrosion.
Surface treatments such as anodizing and cladding help to further corrosion resis-
tance.
Copper-nickel alloys are used in tubings and coils of heater and air-conditioning
systems because of their high thermal conductivity in heating and cooling applica-
tions. Copper–nickel alloys such as 70/30 Cu/Ni and 90/10 Cu/Ni have sufficient
erosion–corrosion resistance in water compared to pure copper.