**7.10 Fretting corrosion**

Fretting is a wear phenomenon enhanced by corrosion. It involves wear of a metal or alloy when in contact with another solid material in dry or humid air. Fretting is the result of abrasive wear surface oxide films, which form a contacting surfaces under load in atmospheric air which is shown in **Figure 10**. The factors which affect fretting corrosion are:


Due to slight motion such as vibration, surface oxide and underlying metal, gets spoiled. The metal particles as a result of wear get oxidized to hard oxides which act as an additional abrasive medium. Further, the motion grinds the oxides particles thus causing wear.

**Figure 10.** *Schematic representation of fretting corrosion.*

**Figure 11.** *Schematic representation of cavitation corrosion.*

## **7.11 Cavitations corrosion**

It is a special type of erosion corrosion which is caused due to the formation of vapor bubbles in a corrosive environment near a metal surface and when the

**11**

*Corrosion Inhibitors*

environments.

spaced pits (**Figure 11**).

**8.1 Nature of the metal**

2.Overvoltage

4.Purity of the metal

5.Physical nature of the metal

6.Nature of the surface film

8.Volatile corrosion products.

**8.2 Nature of the environment**

• Temperature range

• Impurities in water

• Humidity of air

• Influence of pH

7.Solubility of products

*DOI: http://dx.doi.org/10.5772/intechopen.80542*

**8. Factors influencing corrosion**

1.Position of metals in EMF series

3.Relative area of anodic and cathodic parts of the metal

• Presence of suspended particles in atmosphere

• Conductance of the corroding medium

• Formation of oxygen concentration cell

• Flow velocity of process steam

**9. Factors controlling corrosion rate**

• Polarization of electrodes.

• Nature of dissolved gases, dissolved salts, pollutants, etc.

Certain factors tend to accelerate the action of a corrosion cell which includes the establishment of well-defined locations on the metal surface for the anodic

bubbles collapse, attack arises for example, hydraulic turbulence, ship propellers, etc. It is similar to pitting corrosion but the surface is rough and has many close

The extent and rate of corrosion depend on nature of the metals and the

bubbles collapse, attack arises for example, hydraulic turbulence, ship propellers, etc. It is similar to pitting corrosion but the surface is rough and has many close spaced pits (**Figure 11**).
