Tape coatings: A review

Abstract

Coating application is becoming complicated due to increased restriction over environmental regulations, safety hazards, solvent emission and limitations of abrasive cleaning. Protective tapes have emerged a suitable alternative to meet the above demands besides providing efficient corrosion protection to metal surface. The work, therefore, has been taken up to review the performance of various tape coatings and compare with other conventional coatings such as coal tar, FBE, polyurethane etc. Easy application and good insulation properties of tape coatings are observed to put them as the most economic option for rehabilitation of pipeline. Overall coast of PE tape coating application is approximately $30/ft, one third of coal tar enamel and coal tar urethane coatings while average life has been approximated around 20 to 25 years, comparable to other liquid coating systems. The rate of consumption of tapes has been continuously growing in the multiple of 100Mm3 as compared to last twenty-five years. High dielectric constant of tape is found to be responsible for the coating failure as it obstructs CP current to reach under disbonded region of coating and promotes corrosion reaction. Poor designing of protective tapes often permits the diffusion of oxygen, CO2, SO2, etc. through the tape film and react with metal surface in presence of moisture to enhance the corrosion rate. Stress corrosion cracking, microbiological corrosion, pitting and filiform corrosion are dominant types of attack observed under the tape coating primarily due to disbondment of coating. Recent improvements and development in the tape have been highlighted. The methods adopted for application of the tape coating to achieve optimum corrosion protection evolving low application cost has been presented in the paper