Corrosion types that can be prevented with proper care
| Corrosion in Cement | Atmospheric Corrosion |
|
» Porousity remaining after cement solidification » Alakline/Neutral nature of Cement » Atmospheric humidity changes to acidic nature forming Carboxylic Acid » Bonding strength is reduced |
» Corrosion Intensity varies on the type of steel used » Temperature changes weakens the cement bonding » Humidity forms Corboxylic Acid |
| Pitting Corrosion | Stress Corrosion |
|
» Chemical breakdown of passivity of a substance – creation of holes in metal » Corroding substance starts taking the skin of the metal at localized points » Depends on environmental factors such as chloride, oxygen, pH, conductivity, temperature etc. |
» 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 | Galvanic Corrosion |
|
Takes place in shielded metal surface area » Interfacing of pipe couplings » Threaded or riveted connections » Gasket fittings » Spot welded lap joints » Porous welds » Coiled or stacked sheets of metal |
» When totally dissimilar metals remain in contact in a particular atmospheric condition then it leads to galvanic corrosion. » Prevention: Bone Plate and Bone Screws. These should be made with the same metal to avoid any Galvanic corrosion. Use Brass screws in Brassware |
| Inter Granular Corrosion | Erosion Corrosion |
|
When metals are subjected to super heat conditions like 950°F to 1450°F, the grain structure of the steel changes and phenomena of precipitation of metallic compounds of the grain bonding is observed at the corner of the metal. |
When liquid, gas or water flows on metal and the metal is corroded, this type of corrosion takes place, due to the pH of water and the velocity |
| Corrosion causes / factors | Corrosion damages |
|
» Atmospheric Temperature Change » Humidity - Hydrogen and Oxygen in atmosphere » Oxidation with polluted air - Carbon » Acidic conditions in atmosphere » Conversion of pH from Alkaline to Acidic Nature |
» 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) |
| 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 |
« Paints
| Corrosion in Cement |
|
» 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 |
| Annual Corrosion Losses in Rs Crores |
|
| Methods to prevent Corrosion |
|
» Use better grade Steel and Metal Sheets » Improving the quality of base metal by alloying » Surface preparation » Apply coatings before installation » Coating with non reactive metals like Zn & Al » Cladding by welding » Polymeric surface coatings |
VIVID INDIA
B-61, Vivid House, Pushpanjali Enclave
Pitampura, Delhi 110 034, INDIA
+91-11-2702 4086
+91-93 1270 5186
+91-98102 25086
+91-98101 00086
Vivid eMail
Chemistry for better life | © 2002-2023 Vivid™ India. All rights reserved. | Certifications | Photo Gallery | 
Search in Vivid
Search in Vivid