The BTC pipeline will be buried underground during its operational life of 40 or more years. During this period, if the steel pipe comes into contact with water, it will corrode. If it corrodes, eventually, it will leak, or even rupture or explode.

The main method for preventing water getting at a pipeline is to coat the steel pipe in protective coatings, made of plastic or other materials. The 12-metre pipe sections which make up the BTC pipeline are coated in a factory with a 3-layer coating, with polyethylene (a type of plastic) on the outside. However, this doesn't cover the joints between pipe sections where they are welded, as this happens in the field. Therefore, the joints are covered with field joint coatings, which overlap with the factory coatings on the pipe sections on either side of the joint.

In the BTC pipeline, the problem is that an inappropriate material has been selected for the field joint coatings: SPC-2888, which is painted on as a liquid. SPC-2888 does not stick to polyethylene, so will peel away from the outer coatings of the pipes. SPC-2888 also cracks in cold weather. In both cases, water will get into the steel, and lead to corrosion and leaks or ruptures.

See:

Government admits failing BP pipeline was experimental engineering
New article (24 November 2004) by journalist Michael Gillard, published by the Baku Ceyhan Campaign

The full story: Pipeline corrosion threat covered up by BP