Corrosion Reference and Recknor

Corrosion Damages Annual Losses caused due to Corrosion
  • Metallic surfaces - mild sheets (MS)
  • Pipes and GI Pipes
  • Iron Frames and Grills
  • Lower Surface of Vehicles
  • Ships and Boats
  • Bridges and Marine equipments
  • Plastered Cemented Walls (RCC)
  • Roof tops, Asbestos Sheets, Metal sheds
 Annual Corrosion Losses

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Corrosion Causes Corrosion Prevention Corrosion in Cement
  • Humidity
  1. Hydrogen and Oxygen in atmosphere
  • Oxidation with polluted air
  1. Carbon
  • Acidic conditions in atmosphere
  1. Conversion of pH from Alkaline to Acidic Nature
  • Atmospheric Temperature Change
  • Use better grade Steel and Metal Sheets
  • Improve quality of base metal by Alloying
  • Surface preparation
  • Apply coatings before installation
  • Polymeric surface coatings
  • Coat the surface with non reactive metals like Zn & Al
  • Cladding by welding
  • Porousity remaining after cement solidification
  • Alakline/Neutral nature of Cement
  • Atmospheric humidity changes to acidic nature forming Carboxylic Acid
  • Bonding strength in plaster material is reduced

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Types of Corrosion
Atmospheric Corrosion: The Corrosion Intensity varies according to the type of steel used. The Temperature changes due to weather weakens the cement bonding. The environment humidity forms Corboxylic Acid causing Atmospheric Corrosion
Pitting Corrosion: Pitting is caused by the chemical breakdown of passivity of a substance. It causes creation of holes in metal. The Corroding substance starts taking the skin of the metal at localized points. It depends on environmental factors such as chloride, oxygen, pH, conductivity, temperature etc.
Stress Corrosion: The Tensile stress (stretching) on a metal surface results in the exposure of the metal to the atmospheric condition. This is an extension of pitting corrosion.
Crevice Corrosion: Crevice Corrosion takes place in shielded metal surface area such as: Interfacing of pipe couplings, Threaded or riveted connections, Gasket fittings, Spot welded lap joints, Porous welds, and Coiled or stacked sheets of metal.
Galvanic Corrosion: When totally dissimilar metals remain in contact in a particular atmospheric condition then it leads to galvanic corrosion. This can be prevented by using Bone Plate and Bone Screws. They have to be made with the same metal to avoid any Galvanic corrosion. Similarly you can use Brass screws in Brassware.
Inter Granular Corrosion: When Metals subjected to super heat conditions like 950oF to 1450oF, the grain structure of the steel changes. It causes the phenomena of precipitation of metallic compounds. The grain bonding is observed at the corner of the metal.
Erosion Corrosion: When liquid, gas or water flows on metal and the metal is corroded, this type of corrosion takes place. The pH of Water or Gas or Liquid and their Velocity causes erosion.

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Epoxy versus PU System
# Attributes Epoxy Topcoat PU (2 Pack)
1 Material Type Resinous two pack system with Zinc Phosphate / Chromate anticorrosive Single / Two pack Intrinsic High-polymer
2 Technology Old and getting obsolete Latest Two pack polymer technology with inherited anticorrosive
3 Elasiticity Poor Excellent
4 Chemical Resistance Good Excellent
5 Alkali Resistance Good Excellent
6 Toxicity Contains no toxic material Non Toxic
7 Sun Light Exposure Unaffected Unaffected
8 Weather Resistance Good Excellent
9 Effect of Ageing Becomes hard and brittle Completely Flexible (Aliphatic System)
10 Heat Tolerance Temperature Up to 120oC Up to 250oC
11 Flammability Non-Flammable Flammable in uncured condition
12 Burning Rate Slow Slow
12 Passage of Light Semi-opaque Semi-transparent
13 Colour Option Various Various
14 Colour Options Various Various
15 Tensile Strength Poor Very High
16 Thermal Insulation Poor Very Good
17 Water Resistance Poor Excellent
18 Water Resistance Poor Excellent
19 Typical coverage per litre for single coat 70 - 80 sq ft 1. 80 - 90 sq ft on Rough Surface
2. 150-300 sq ft on Wood, Metal & Smooth Surface.
20 Thinning Material Costly Epoxy Thinner MTO or Neptha
21 Pot-life (Ready to apply condition) Only 90 to 110 minutes single pack - 90 to 110 minutes
2 Pack - 40 to 45 minutes
22 Shelf Life 12 Months 24 Months
23 Depth per coat 35 to 40 Micron 30 to 55 micron in single pack
up to 100 micron in two pack system

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