B2B Purchase – July 2019

chemicals & coatings opinion

58 B2B Purchase July 2019

Criteria for selection

The criteria for selection of right quality for

corrosion protection coating or treatment depends

on numerous factors like life of treatment required

and the environment to which it is exposed as we

know that when the reinforced concrete or metal,

is exposed to corrosive environments, it tends to

have chemical reactions with the air or water or

chemicals. The effects of corrosion become evident

on the surfaces of these materials. For instance,

after putting the iron into a corrosive atmosphere

for an extended period, the iron starts rusting due

to oxygen interaction with water on the iron’s

surface. Therefore, metal equipment lacking any

preventive (anti-corrosive) measures, may become

rusted. There are several methods for preventing

corrosion, especially in marine applications.

Anti-corrosion measures are of importance in

environments where high humidity, mist, and

salt are present. It is important to have a detailed

chemical analysis of the metal or treatment

surface and coating or anti-corrosive material, to

determine the efficacy of the treatment. Corrosion

issues can be associated with the conditions

of operations like cooling tower would require

treatment to protect them from microbiological

organisms and wet and dry condition of surface,

especially in the splash zone and basin area in

a natural draft cooling tower. Today, corrosion

amounts 6-7 per cent of the GDP.

Corrosion of structural steel

The corrosion of structural steel is an electrochemical

process that requires the simultaneous presence

of moisture and oxygen. Essentially, the iron is

oxidised to produce rust, which occupies about six

times the volume of the original material. The rate

at which the corrosion process progresses depends

on several factors, but principally the ‘micro-

climate’ immediately surrounding the structure.

Corrosion of steel in concrete structures

The water penetration helps corrosion of the steel

reinforcement. As the rust has more volume than

the original steel bar, the rust causes tension in

the surrounding concrete. As the cover of concrete

is limited on the outer side, the resultant tensile

force causes cracks formation and the cracks

permit easier entry of water and oxygen to form

more rusting. Resulting leads to increase in volume

and the cracks in concrete get wider and wider. The

surrounding concrete becomes partly disintegrated

which finally causes spalling.

Corrosion resistant coatings

Corrosion resistant coatings ensure metal

components have a longer life. Metal coatings are

idly used coatings in the industry. The function

of the coating is to act as a barrier that inhibits

contact between chemical compounds or corrosive

materials with the metal housing.

STP Ltd was established in 1935 as a bitumen

and tar based company and diversified into

construction chemicals, anti-corrosive treatment

and many other products, STP Ltd brings decades

of experience to the application of corrosion

Anti-corrosive coatings and treatments