The document discusses corrosion of steel and methods for corrosion protection. It first covers the causes and types of corrosion including atmospheric corrosion. It then describes some basic methods for corrosion control like coatings, alloying metals, and galvanizing. Organic coatings and passive rust coatings are highlighted as major protective methods. The document also discusses research on corrosion prevention techniques like coatings, galvanizing, and alloying metals with corrosion resistant elements. It notes that corrosion costs the US billions annually and degrades coatings over time through processes like blistering and undermining. Finally, it summarizes some conclusions that coatings, galvanizing, and alloying can effectively prevent corrosion when used appropriately.

1. ENGINEERING MATERIALS-II
CORROSSION PROTECTION OF STEEL
EFFORTS BY: DAVE MADHAV UC(1416)
GUIDED BY: ANAL SHETH

2. The abstract paper reviewed includes the following aspects:
 Causes of corrosion
 Atmospheric Corrosion
 THE basic methods for corrosion control and corrosion protection
 Corrosion cost
 Research on corrosion and its prevention
 Corrosion Protection by Coating
 Degradation of Organic Coatings
 Some conclusions as per research paper

3. Causes of corrosion
 Corrosion is defined as the deterioration of a material, usually a metal, because of a
reaction with its environment and which requires the presence of an anode, a
cathode, an electrolyte, and an electrical circuit.
 Steel corrodes when exposed to myriad conditions including outdoor atmosphere.
Corrosion of steel
o Mild Steel:
 Carbon steel (mild steel) is the most prone to corrosion
o Weathering Steel
Weathering steels comprise a group of high strength, low alloy steels containing
alloying elements to give an enhanced resistance to rusting compared with carbon
steels
 These steels have 1–2.5 % of alloying elements (Cr, Cu, Si, and P) and have a
tendency to form rust at a rate depending on the access of oxygen in the presence of
moisture and air.

4. Atmospheric Corrosion:
• Atmospheric corrosion is an electrochemical process with the electrolyte being a thin
layer of moisture on the metal surface.
• The composition of the electrolyte depends on the deposition rates of the air
pollutants and varies with the wetting conditions.
•The factors influencing the corrosivity of atmospheres are gases in the atmosphere,
critical humidity and dust content
• During atmospheric exposure, steel gets a reddish brown corrosion product consisting
of different constituents.
• In weathering, steel rust formed on atmospheric corrosion in different environments is
composed of crystalline compounds like haematite, magnetite and oxyhydroxides of
iron like goethite, akaganeite, lepidocrocite and feroxyhite apart from amorphous
ferric oxyhydroxide rust

5. The basic methods for corrosion control and corrosion protection:
1. Corrosion Protection by Coating:
• The major protective coatings applied to structural steelwork are paints, metal
coatings and combinations of both.
• The protection methods can be divided into three categories like applying organic or
inorganic coatings, controlling electrode potential to make metal immune or passive
by adding alloying elements in steels to promote formation of passive layer and
addition of corrosion inhibitors to the environment
a) Passive Rust Coatings :
• Passivity is due to the presence of a thin film which isolates the metal surface
from a corrosive aqueous environment
b) Organic Coatings:
• Organic coatings used on steel provide an effective barrier protection by
isolating steel from the attacking species.

6. Corrosion cost:
• The total national yearly cost of metallic corrosion in the United States was
estimated at $275 billion, or 3.1% of the U.S. gross domestic product (GDP) of $8790
billion, in 1998 .This total includes replacement costs and lost production costs as
well as the decrease in lifetime and the expected replacement value of a given
component subject to damage by corrosion. The cost of corrosion also includes the
means by which the effects of corrosion are mitigated, such as the use of cathodic
protection, inhibitors, alternative materials of construction, overdesign, and
protective coatings

7. Research on corrosion and its prevention:
• Coating the metal, in order to interpose a corrosion resistant
coating between metal and environment.
• Alloying the metal to produce a more corrosion resistant alloy, e.g. stainless steel,
in which ordinary steel is alloyed with chromium and nickel.
• Hot-dip galvanizing is a process that involves immersing the steel component to be
coated in a bath of molten zinc (at about 450°C) after pickling and fluxing, and then
withdrawing it
• Thermally sprayed coating of zinc, aluminium, and zinc-aluminium alloys can provide
long-term corrosion protection to steel structures exposed to aggressive environments
• The elements Cu, P, Cr and Ni have all been shown to improve resistance to
atmospheric corrosion, so they are coated on steel as a inhibitor

8. Corrosion Protection by Coating
• The major protective coatings applied to structural steelwork are paints, metal
coatings and combinations of both
1. Passive Rust Coatings:
• Passivity is due to the presence of a thin film which isolates the metal surface from a
corrosive aqueous environment.
2. Organic Coatings
• Organic coatings used on steel provide an effective barrier protection by isolating
steel from the attacking species
• Coatings which contain large quantities of metallic zinc provide corrosion protection
by galvanic action
• An important property of a coating is its resistance to water penetration and two
related properties are coating dielectric strength and coating resistance to ionic
movement.
• Water penetration in coating decreases the dielectric strength, resistivity and makes
the coating less insulative.

9. Degradation of Organic Coatings:
• There are several types of corrosion found beneath organic coatings and these are
blistering, filliform corrosion, rusting, anodic undermining and cathodic
delamination
• Blistering is one of the first signs of breakdown in the protective nature of the
coating
• The blisters are local regions where the coating has lost adherence from the
substrate and where water may accumulate and corrosion may begin
• Oxygen penetrates through the coating and leaching of ionic materials from the
interface.

10. Some conclusions as per research paper:
 Hydrophobization of the reinforced concrete elements provides a good protection of
the reinforcement steel under normal atmospheric conditions and periodical
wetness.
 The corrosion of the reinforcement steel in the concrete crevice area is the result of
the change in its passive state under the action of the corrosion activators.
 The results show that both primers offered significant protection against atmospheric
corrosion
 Pitting corrosion rates were significantly higher than the general corrosion rates.
 It was also seen that oxygen or carbon contained in the aerating air speed up the
corrosion rates of copper as well as iron.
 Many convention corrosion prevention methods like use of coatings, galvanizing can
be effective for the corrosion prevention
 In some cases, the additions of 0.3 % copper to carbon steel can reduce the rate of
rusting to a greater extent

11. Reference:
1) STUDIES AND RESEARCH WORK ON THE REINFORCEMENT STEEL AND
CONCRETE SURFACE CORROSION PROTECTION METHODS
Gheorghe CROITORUScientific Research Centre, Republic of Moldova, e-
mail:gcroitoru@mail.ru (Research paper)
2) A Review on Studies and Research on Corrosion and Its Prevention
Sunil J. Kulkarni E-ISSN: 2349-9788; P-ISSN: 2454-2237 (Research paper)
3) Corrosion of Constructional Steels in Marine and Industrial Environment
(ENGINEERING MATERIAL VOL-1)
Jayanta Kumar Saha