Just like the name suggest, the main use if tank liners is to ensure that anything that may be inside a tank is not contaminated if it happens that the material that has been used to make the tank starts to corrode. This is made possible by ensuring that the tanker liners are used in lining the inside surface of the tank. The liners are used for both home and industrial storage systems to provide a scenario where everyone is staying healthy with tanks liners.
The foremost tank maintenance site in Australia, http://atmtanks.com.au/ observes the main reason behind using tanker liners in the case of storing drinking water is to ensure that all the particles that may come from the tank do not infect the water. When you consider a situation where plastic lining gets to be used in a corrugated iron tank what comes into contact with the water is usually the polymer plastic. What this means is that the water gets automatically contaminated making it completely unsafe for use. The recommendation is always that all tanks should be lined.
Corroding has always been the main reason that liners are used. This is because immediately a tank rusts it precipitates a situation where we expect corroding. Rusting comes with two main disadvantages; it does not only corrode the tanks but also contaminates the water with toxins making it quite harmful for domestic use. The side effects of these toxins could be quite severe as they have been known to cause cancer if using this contaminated water is persistent for a long period of time. Important to note is that if a tank is lined and corrosion happens to occur then the water is still safe for use.