Page 39 - Realm Catalog

Like death and taxes, corrosion

THE CORROSION CHALLENGE is something we hope to avoid;
but ultimately it is something we
That India is geographically surrounded by a 7000 km. Coastline is a fact.
That India is investing in industries and construction, involving metal usage in a big way, must learn to deal with.
is also a fact.
Put the two facts together and the conclusion is inevitable – that corrosion and its various
fallouts will continue to be a major source of worry for the construction industry in India.
So let’s acknowledge the truth – that corrosion is a fact of life that cannot be wished away.
So what exactly is this corrosion that strikes so much fear in the construction industry?
Corrosion is an electro-chemical action, where one metal is changed into a chemical
or is simply eaten away. Thus in the presence of air, water or salt, non-precious metals
like Steel, Zinc, Aluminium and Copper undergo a process called oxidation (rusting),
which slowly disfigures the metals, rendering them unsafe and useless. Humidity and air
pollution are the other factors that contribute to hastening the corrosion process.

THE DIFFERENT TYPES OF CORROSION

GENERALISED CORROSION (OXYGEN TYPE) prevention when a less noble metal like zinc is acid, acetic acid, etc. are found in the vicinity THE COST OF CORROSION
This is the most common and prevalent type of used to protect the carbon steel. of industrial plants, while chloride and sodium Corrosion significantly affects the structural
corrosion, where humidity and moisture results BIOCHEMICAL CORROSION chloride especially, are common atmospheric integrity of a construction. Premature deterioration
in electrolytic reactions developing on the steel When metals dissolve in acid and caustic pollutants in coastal regions. or failure, results in greater maintenance, repair
surface, leading to progressive corrosion. The rate solutions of different strengths, chemical AERATION CELL CORROSION and replacement of damaged equipment. Besides
of corrosion increases rapidly in the presence of corrosion occurs because metals tend to combine An oxygen deficiency can develop in a damp this, costs also escalate, due to lost production
other pollutants and raised humidity levels. with oxygen to form oxides. The less noble the thermal insulation or in any other situation when hours and increased downtime of equipment; all
GALVANIC CORROSION (HYDROGEN TYPE) metal, the stronger the tendency. The attacking moisture is trapped and gathers pollutants. arising from corrosion problems. Talking of cost,
In this case, the combination of two dissimilar acids often come from the atmosphere. For Corrosion will occur in the area of restricted in India, the cost of corrosion has been estimated
metals with an electrolyte (moisture) is all that is example, the sulphuric acid that comes from the oxygen supply, even in a non-polluted area of high to be 3% of its GDP and that the roofing industry
needed to form a reaction, where the less noble sulphur dioxide emissions from burning fossil PH value. Where other pollutants are present as in particular, incurs a loss of no less than Rs. 360
metal migrates and dissolves into the solution. fuels, is found in urban and industrial areas; in a lower PH value are, the corrosion will increase. crore annually.
Galvanic corrosion is also used for corrosion nitric oxides, chlorine, hydrogen chloride, formic