The characteristics, generating process and innuencing ractors of lamination defect of sendfinished pipe are analyzed based on pierced high temperature alloy blank, and the generating mechanism of lamination defect is discussed.

The results show that the elements segregation was the main reason for the lamination defect During the continuous casting process,inclusions of MnS,TiC,NbC were formed because of elements segregation of S,Mn,Nb,Ti at the center of the steel.

The effect of coating defect on the permeation behavior of corrosive ions through coatings,coatings degradation,the corrosion behavior of substrates are discussed based on the review of the study field which included coating defects,blistering and wet adhesion etc.

The influence of soil resistivity and coating defects on IR drop error in cathodic protection(CP)potential measurement was studied by theoretical methods.