Corrosion Basics: Tank and Containment Linings

Some of the most critical uses of protective coatings involve service conditions that require the use of coatings as linings. They may be the same coatings that are used in atmospheric or underground service, but they are usually specially formulated for three specific purposes:

1) To protect the substrate (steel, aluminum, concrete, or other materials) from attack by the liquid being stored inside the tank or temporarily stored inside a containment structure

2) To protect the liquid being stored from contamination by the substrate

3) To restore structural integrity to an old tank, while meeting the requirements for protection of the substrate from corrosion and the liquid in storage from contamination

All coatings are permeable to some degree. The choice of coatings as tank linings requires a much greater knowledge of the properties of the liquid being stored and the ability of the coating to withstand permeation by that liquid than would typically be required for any coating being applied in atmospheric service.

Choosing a Tank or Containment Lining

Few project managers have an in-depth knowledge of the suitability of various tank linings when placed in immersion of aggressive, penetrating liquids. It is possible to review the product data sheets of several global scope and specialty scope manufacturers to get a general idea of which linings might work in a given situation. However, this approach is risky in that the product data sheets, of necessity, must be quite general in nature. There are three recommended alternatives that will provide choices with better chances of success in a given application:

1) Comparative side-by-side testing of candidate systems in a laboratory program that simulates, to the best extent possible, the service conditions expected in that particular tank. This takes time but can provide very good indications of a lining’s resistance to permeation by a particular liquid for a given period of time at a stated storage temperature.

2) If time does not allow for comparative laboratory testing, the candidate coating manufacturers can be requested to provide their chemical suitability tables for the products that are being considered for a particular tank. Although this normally is limited to specific testing for specific time frames such as 30 and 60 days, it often provides reliable guidelines about the performance characteristics of each product. In addition, these suitability tables normally include some very valuable precautions regarding immersion based on the pH, temperature, etc., of the chemicals. Some very valuable information is normally available about cleaning chemicals, procedures, and recovery times between different cargoes.

3) Review selected case histories of tank linings used in similar services. This can be very valuable as it provides longer-term results. However, when doing so, the project tank and containment linings manager must be careful to confirm that the service conditions are truly similar to the expected service conditions. He or she must also be careful to confirm that the product shown in the case history is still formulated the same as it was when that case history was conducted. Volatile organic compound requirements have caused changes in products to achieve higher volume solids that can, and have, drastically altered the chemical resistance of some products.

This article is adapted by MP Technical Editor Norm Moriber of Mears Group, Inc. from The Protective Coating User’s Handbook, Louis D. Vincent (Houston, TX: NACE International, 2010), pp. 147-148.

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