Corrosion Rates of Steel Piles Protected by Petrolatum Tape

This paper summarises available data from existing case studies on the effectiveness of petrolatum tape to protect steel piles from the effects of corrosion. The paper also compares this data to a site investigation undertaken in 2019, which obtained thickness measurements on a pile wrapping system installed over 30 years ago. The data has been used to underpin the 35-year life-extension of a safety critical maritime asset (more than 1,000 Circular Hollow Section “CHS” Piles) with expected through life savings on maintenance and inspection.

A small number of laboratory tests and site studies on the effectiveness of the petrolatum tape have been undertaken over short periods of time (weeks or months) and the results extrapolated to provide the annual corrosion rate. However, at the time of writing there is no published field data for the long-term corrosion rates of steel CHS piles protected by petrolatum tape.

This paper presents the site data from a UK case study in which piles have been wrapped with petrolatum tape for over 25 years. The site data has then been compared with the published short-term corrosion rate data. When considering the use of the tape system in design or life-extension projects, the corrosion rate can be considered to be a maximum of 0.005mm/year based on a UK site. This assumes that an effective maintenance regime has been implemented to ensure that the tape is not exposed to mechanical damage. Therefore, a petrolatum tape system can be effective at obtaining and extending the design life of marine structures.