**5. Corrosion**

across the heat exchanger. Many types of fouling can occur on the heat transfer surfaces, for examples, crystallization fouling, particulate fouling, corrosion fouling, chemical reaction fouling, biological fouling and solidification fouling [14]. Fouling can have a very costly effect in the industries which eventually increases fuel usage, interrupts operation, production losses

The fouling is formed in five stages which can be summarized as initiation of fouling, transport to the surface, attachment to the surface, removal from the surface and ageing at the surface [16]. There are a few parameters influencing the fouling factors, such as pH [9], velocity [17], bulk temperature of fluid [18], temperature of the heat transfer surface, surface structure [19]

The overall fouling process is usually considered to be the net result of two simultaneous sub processes: a deposition process and a removal process as shown in **Figure 2**. As illustrated in

and enhances maintenance costs [15].

196 Heat Exchangers– Advanced Features and Applications

and roughness [20, 21].

**Figure 2.** Overall fouling process [22].

**Figure 3.** Fouling resistance against time curves [22].

Environment features such as soil, atmosphere, water or aqueous solutions commonly attack general metal and alloys. The deterioration of these metals is known as corrosion. It is agreeable that corrosion happens due to electrochemical mechanism. Premature failures in various equipment are caused by corrosion in most commercial processes and engineering operations, leading to unwanted issues. This includes pricey breakdown, un-schedule shutdown and increases in maintenance cost.

This downtime worsens in fields such as chemical industries, oil refining, sea and land electric power plant, paper manufacture, air conditioning, refrigerator, food and liquor manufacturing. Hence, general info and mechanism of corrosion will bring great interest to public and

**Figure 5.** Factor influencing corrosion [25].

industry [24]. The corrosion process is affected by various parameters as show in **Figure 5**. Hence, these criteria should take consideration into the design basics of heat exchangers.
