Page 204 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

182 CORROSION CAUSES

TABLE 3.14 Major Input Items and Farm Production Expenditures on 1997
Item Percent of Total Expenditure
Chemicals, fertilizer, and seeds 15
Feed 14
Fuel 3
Farm services 13
Interest, taxes 10
Livestock 8
Machinery, vehicles 7
Labor 10
Rent 10
Supplies, repair and construction 10

Fertilizer tanks are susceptible to pitting and erosion–corrosion in the acetic acid
solutions used in fertilizers.
Corrosion problems occur in milking process systems because of the moisture,
sanitizing chemicals, and animal respiration. Corrosion problems occur because of
hot water cycles and wash water used to clear milking equipment.
Agricultural fumigants, such as methyl bromide and phosphine, are used to
disinfect food products. Phosphine in combination with carbon dioxide and humidity
is corrosive to copper and electronic and electrical equipment in food processing area.
Agricultural buildings that house livestock require special care in selecting wiring
materials, wiring methods because of the corrosive dust, gases, and moisture. Corro-
sion of metallic conduit, boxes, and fixtures lead to electrical system failure. Accel-
erated corrosion because of condensation occurs on electrical panels that are not
properly designed.

3.28 THE FOOD PROCESSING SECTOR
The corrosion environment in the food and beverage industry involves moderately to
highly concentrated chlorides, often mixed with significant concentrations of organic
acids. The water side of the processing equipment can range from steam heating
to brine cooling. Purity and sanitation standards require excellent corrosion resis-
tance to pitting and crevice corrosion. Sulfating agents producing sulfur dioxide when
used to treat foods are sodium sulfite, sodium bisulfite, potassium bisulfite, sodium
metabisulfite, and potassium metabisulfite. All of these additives are corrosive to food
processing equipment.
Underdeposit corrosion is likely to occur in cooling systems where scales or
foulants exist. The presence of general fouling and scales can cause the formation of
a differential cell, which begins the process of corrosion because of the difference
in oxygen concentration at the metal surface beneath the deposit and the oxygen
concentration in water, a differential cell forms, resulting in the corrosion reaction.