Corrosion Protection Improvement-Wind turbines

Corrosion:

Corrosion is a natural process, which converts a refined metal to a more chemically-stable form, such as its oxide, hydroxide, or sulfide. It is the gradual destruction of materials by chemical and/or electrochemical reactions with their environment.

Factors which Affect Corrosion

The main factors which affect corrosion are

1.   More the reactivity of metal, the more will be the possibility of the metal getting corroded.

2.   The impurities help in setting up voltaic cells, which increase the speed of corrosion

3.   Presence of electrolytes in water also increases the rate of corrosion

4.   Presence of natural water increase rusting of iron.

5.   When the iron surface is coated with layers of metals more active than iron, then the rate of corrosion is retarded.

6.   A rise in the temperature within a reasonable limit) increases the rate of corrosion.

Types of Corrosion

1.   Dry corrosion

2.   Wet corrosion

1.   Dry corrosion: It is also known as chemical corrosion. Corrosion is due to direct chemical attack of metal surface by the atmospheric gases.

a.   Oxygen

b.   Sulphur dioxide & Nitrogen etc. ,

2.   Wet corrosion: It is also known as electrochemical corrosion .Such type of corrosion due to the flow of electron from metal surface anodic area towards cathode area through a conducting solution.

Methods to Control Corrosion

There are five methods to control corrosion

1.   Material selection

2.   Coating

3.   Changing the environment

4.   Changing the potential

5.   Design

Coating Methods:-

A Coating is a covering that is applied to the surface of an object. The purpose of applying the coating may be safeguard of material from moisture.

Coatings may be applied as liquids, gases or solids.

Types of coating processes:-

1.      Chemical and electrochemical techniques

2.      Spraying

3.      Roll-to-roll coating processes

4.      Physical coating processes

5.      Vapor deposition.

Two important coating Methods:-

1.  Lacquer coat

2.  Wax coat

1. Lacquer Coat:-

 

Lacquer coat application is recommended for stainless steel components and fasteners, electrical components, and pre-coated mechanical components such as hydraulic aggregate, brake caliper, where transparent coat is needed for aesthetic of WTG.

Lacquer Coat procedure:- 

Step: 1

Clean the surface and nearby working area using degreasing chemical /

solvent to remove grease, oil and dirt.

               Step: 2

Remove rust and loose paint flakes from surface using sand paper, wire brush, scrapper, and power tools, whichever is most suitable and efficient. Use only emery paper for rust removal, surface preparation of panel inside components. Below are the tools found suitable for cleaning rusted surface for lacquer application.

               Step: 3

Drilling machine with metal wire wheel: Useful for cleaning rust from corners and components having complex shapes (Corners in casting, fabricated components, brackets, coupling parts, nacelle fan, etc.)

               Step: 4

Take an amount of component (base) in a container which can be utilized within specified pot life. Add proportionate amount of component (curing agent) and stir well the mixture till it becomes homogeneous.

Before lacquer application, ensure surface is dry and free of contamination.

              Step: 5

Apply lacquer mix on prepared surface using painting brush or roller of suitable size.

               Step: 6

After completing lacquer application, let the surface to dry. When surface becomes touch dry, inspect the surface visually for any uncoated spot of lacquer and measure DFT (Dry film thickness).

 

Minimum required DTF is 25-50µ.