文档介绍：8243—Prelims—10/11/2006—18:40—CRCPAG—14180—XMLMODEL B–pp. 1–18
Preface
Corrosion is bothcostlyand dangerous. Billionsofdollars are spent annually
for the replacement of corroded structures, machinery,ponents,
including metal roofing, condenser tubes, pipelines, andmanyother items.
In addition to replacement costs are thoseassociated with preventive
maintenance to preventcorrosion, inspections,and theupkeep of
cathodically protected structures and pipelines. Indirect costs of corrosion
result from shutdown, loss of efficiency,and product contamination or loss.
Although theactualreplacement cost of an item maynot be high,the loss
of production resultingfromthe need to shut down an operationtopermitthe
replacementmay amount to hundreds of dollarsper
or pipeline develops aleak, productislost. If theleakgoesundetectedfor
aperiodoftime, thevalue of thelostproduct couldbeconsiderable. In addition,
contaminationcan result from theleaking material,requiring cleanup, andthis
canbequite expensive. When corrosiontakes place, corrosionproductsbuild
up,resultinginreduced flowinpipelines andreduced efficiencyofheat
transfer in heat costs. Corrosion
products mayalsobedetrimental to thequality of theproduct beinghandled,
making it necessarytodiscard valuable materials.
Prematurefailure of bridges or structures because of corrosioncan also
result in human injury or even loss of life. Failures of operating equipment
resulting from corrosioncan have the same disastrous results.
When all of these factors are considered, it es obvious why the
potential problem of corrosion should be considered during the early design
stagesofany project, and whyitisnecessary to constantly monitor the
integrity of structures, bridges, machinery,and equipment to prevent
premature failures.
To cope with the potential problems of corrosion, it is necessary to
understand
1. Mechanisms of corrosion
2. Corrosion resistant