(1) Source of evaluation of external coating
Literature states: "steel surface condition is called environment that can coating and soil pipe insulation four weeks, four weeks the tube surface soil conditions are different and therefore the corrosion protection layer of the pipe is an important barrier to prevent soil erosion. " This is the basic starting point of the evaluation outer coating performance. Joe Leighton British company discussed from two different perspectives pipe coating system: European perspective is to make it able to withstand moisture, prevent corrosion, it is the "barrier" point of view. From this point of view it had a "PE" protective layer method. The North American point of view is to make it possible to oxidation resistance, chemical resistance and resistance to negative release properties to prevent corrosion, which is the "glue" point of view. From this point of view, resulting in a "FBE" law protective layer.
Another current trend is to the two foreign viewpoints known as "barrier" and "bond" combined, the development of a new point of view, the forthcoming European "PE" barrier protection layer method and North America "FBE" protection layer method to combine the development of an integrated-type "3PE" law protective layer. The new ideas, new technology, new methods in our country has begun to promote the application.
(2) the basic functions of the outer coating of steel
There are two aspects:
First, make the ERW steel pipe surface from electrochemical corrosion, bacterial corrosion protection of soil basic physical media,
Second, resist the soil medium move creep stress, basic mechanical protection method static stress and abrasion strength and structure and so on.
