FAQ

• Pipelines and piping networks,
• Water treatment plants,
• Above and underground storage tanks (internal & external)
• Ship and boat hulls.
• Offshore Platforms.
• Reinforcement bars in concrete structures.
• Jetties & harbors.

Electrochemical corrosion is generally caused when two dissimilar metals (by material or environment) are submerged in an electrolytic substance such as water (fresh or sea), soil, or concrete. A pathway is created through which free electrons move from the more active metal (anode) to the less active metal (cathode).

A reaction at the surface of the cathode allows oxygen to combine with the steel to produce ferrous hydroxide, i.e., rust.

For corrosion to happen, four elements must be present: a host site from which current flows, a destination site where no current flows, a medium capable of conducting current (such as water, concrete, or soil), and a return path between the host and destination site.

There are two basic types of cathodic protection: galvanic (or sacrificial) and impressed current cathodic protection. It differs from using.

• A galvanic anode remains active through its lifetime which typically varies from 10 to 20 years.
• An impressive current system is typically designed for a lifetime of 25 to 30 years.However, where anodes cannot be easily replaced the design can be increased to over 50 years.

The potential of an electrode is measured with the help of reference electrode. Depending upon the structures, various electrodes are used.

• Copper-copper sulphate electrodes – structures in contact with fresh water and soil.
• Silver/silver chloride/seawater electrodes – seawater applications.

Although cathodic protection has several significances, there are a few limitations to the use of cathodic protection. Some of them have been briefed as under:

• Production of Hydrogen: Production of atomic hydrogen may occur as a side effect if the cathodic protections are applied in an improper manner. Thus, produced hydrogen in eventually absorbed by the protected metal, which further leads to hydrogen embrittlement in very hard metals. The hydrogen atoms can react with the metal surface to form hydrogen gas leading to hydrogen embrittlement.
• Cathodic Disbanding: The protective coating from the cathode is disbanded because of the formation of hydrogen ions on the surface of the cathode.
• Cathodic Shielding: The phenomena of cathodic shielding occur because of the high electric resistivity of the film backings used in various processes. They are used in steel pipelines. The electrolytes are shielded from reaching the destination hence disturbing the efficiency of the entire process.

It is highly resistant to mineral acids, alkalis, salts, and micro-organisms and highly impermeable to water, water vapor and gases. Used for the protection of buried or exposed pipes, rods, cables, valves, and metal fittings from corrosion.

Cleaning is the first step to ensuring that you have a dirt-free, dust-free, oil-free, and optimal substrate for the sealant to develop adhesion to.

Heat-shrinkable sleeve is a corrosion protective coating for pipelines in the form of a wraparound or tubular sleeve that is field-applied. It can be applied depending on operating Temperature, Thickness and other features.

Polyethylene Mechanical anti corrosion tape is Cold applied tape coating system for corrosion protection of Oil, Gas, Petrochemical, and Wastewater underground or overhead pipelines. The outer-layer tape backing shall be compounded so that it will be resistance to outdoor weathering.

The corrosion coupon, made of a material of interest with designed weight and shape, is installed and exposed to the corrosive environment for a duration of time and then retrieved for after-corrosion weight measurement and inspection on the corroded coupon.

Corrosion Monitoring Techniques:

• Corrosion Coupons (intrusive)
• Electrical Resistance (ER) (intrusive)
• Inductive Resistance Probes (intrusive)
• Linear Polarization Resistance (LPR) (intrusive)
• Electrochemical Impedance Spectroscopy (EIS) (intrusive)
• Electrochemical frequency modulation (intrusive)