Plate heat exchangers are used in Ocean Thermal Energy Conversion plants, dairy unit and lube oil cooling plants where a small D T is available for transfer in the system. They are widely preferred because of their compactness, surface area temperature approach upto 1° C. Absolute heat exchanger cleanliness is essential for the performance of these exchangers.

Numerous microscopic studies have described the development of biofilm on surfaces immersed in marine waters. The biofilm development begins with the adsorption of dissolved organic matter followed by the colonization, attachment and growth of microorganisms, and adsorption of particulate matter.

Various studies have indicated that multispecies biofilms have characteristic architecture and behave very much like 'quasi-tissues', exhibiting remarkable metabolic co-operativity among constituent microcolonies and a primitive type of homoeostasis.

On the basis, there is little a difference between the chemical analyses of ductile and gray cast irons that the corrosion resistance of the two materials also would be similar. However, there is disagreement as to whether or not ductile iron should have better corrosion resistance than has gray cast iron because of the spheroidal morphology of the graphite nodules.

Microbiologically influenced corrosion (MIC) is caused by the presence and activities of microorganisms in biofilms on the surface of the corroding material. Most materials, including metals, polymers, glass and ceramics can be degraded in this manner.

Without properly characterizing the failure attributes, corrosion debris, or environment involved in the failure, the root cause of the failure may be coming from an unexpected source, and may remain to cause the replacement components to fail.

Closed water systems are carefully designed to create precise and adaptable environmental conditions within buildings or process plant. The design necessitates the use of small bore control and regulating valves. If corrosion debris, installation debris or microbes are present these orifices may become blocked or restricted and the system will not operate to design parameters. Ultimately if systems are not cared for the pipework and fittings may fail prematurely due to corrosion and other contributory factors. So, water quality and water treatment are very important.

An unusual and perhaps unexpected corrosion problem can be caused by bacteria. As one of the oldest groups of organisms on the planet, bacteria have evolved to survive even in extreme environments.

When two dissimilar metals are in contact, or in close proximity with a conducting fluid in between, an electrochemical cell can be formed that leads to the more reactive metal becoming an anode and the less reactive metal a cathode. This kind of corrosion is known as galvanic corrosion. It is not uncommon, since metals are often coated with others of different E0, and different metals are often in close contact with a common electrolyte.

Structural materials can be attacked by environments. Although they do have specific connotations, they are frequently used as blanket terms for material deterioration. They are degradation, dissolution and corrosion. 

• Degradation: loss of strength of non-metals such as wood, rope or textile.
• Dissolution: removal of material in solution owing to the attacking medium.
• Corrosion: attack of metallic materials.

Many failures occur after a product has been in service for some time: such as the wear of a car tyre, or corrosion of the car body itself. It is also possible for components to fail because of a combination of a manufacturing defect with the applied loading or with the environmental conditions during use.

In many cases component failure is because something has reached the end of its working life due to a slow-acting failure mechanism: car tyres wear slowly and will eventually burst if not replaced; the filament in a light bulb slowly loses material until it cannot sustain the applied voltage and melts.

Microbial influenced corrosion can be caused for various microorganisms. Under humid conditions, Thiobacillus bacteria (microorganism) absorb hydrogen sulphide (H2S) gas on the sewer walls and excrete the corrosive acid which attacks concrete.

Zinc has been used as a sacrificial anode to cathodically protect ship’s hulls for more than a century now. It has become a common practice to use cathodic protection either alone or in combination with coatings for buried pipelines, storage tanks and offshore structures.