Inhibiting Ferrous Oxidation on
Pad-mounted Transformers (PMT)
Rashidat Oyegunle
Energy Systems Engineering
Lehigh University
Introduction
Transformers are key operational infrastructures that aid the successful transfer and delivery of power within the electrical grid. While there are
different types of transformers, pad-mounted transformers (PMTs) are the key focus of this project. Situated in a box-like steel tank on a concrete
pad at ground level, PMT tanks are susceptible to rust as a result of the direct exposure to the environment. Thus, it is important to ensure upmost
integrity for PMT casings for continuous reliable electric service, product longevity, public safety, and capital gain. Coatings serve as sacrificial or
barrier mediums for reducing a surface’s corrosion rate. Consequently, a highly resistive coating will increase the PMT tank’s enclosure integrity
from corrosion and other chemical and physical exposures. The project highlights old and new coating methods such as alkyd, epoxy,
polyurethane and the newly emerging superhydrophobic and rust convertor coatings. Through literature review and expert consult, this research
analyzes each coating based on the following properties: ease of application, longevity and degree of protection.
PPL EU’s Pilot Inspection Study
PPL EU’s pilot inspection study on 600 PMTs initiated the scope of this
project.
• Samples population were randomly selected from six service regions
• 542 of 600 PMT tanks exhibited some level of corrosion
• Stage (1) & (2) of the six stages of corrosion: apparent rust spots
and cluster of spots
• Question: How to prevent further damage on PMT tanks to avoid
premature replacement of the entire unit before fulfilling its expected
operation life span?
Research Objectives
The project is divided into two phases. Objectives for phase I and II are
listed below:
Phase I:
• Analyze barrier coating products
• Evaluated PMT coating standards
Phase II
• Design an accelerated aging experiment to test the proposed coatings
• Determine the feasibility of re-coatings of PMTS
• Determine the most suitable and feasible coating through comparison
of various factors
Proposed Coatings
Old Coating Methods
① Alkyd
② Epoxy
③ Poly Urethane
A PMT tank without corrosion vs. PMT tank with evidence of early stages of corrosion
Photo Credit: Osmoses Utilities Services (from PPL EU’s PMT pilot inspection)
Resistance Level of Coating Inhibitors
Anticorrosion
Surface Wettability
Adhesion
Alkyd
High
High
Medium
Epoxy
Medium
High
Medium
Poly Urethane
Low
High
Medium
Superhydrophobic High
Low
High
Laboratory Testing Guideline
Safety &
Aesthetics
Economic
Losses
Disruptive Coating Methods
④ Superhydrophobic
⑤ Rust Convertor
Longevity
System
Reliability
• Applicable for
all field
applications
• Paint, spray
or brush
application
Paint Coating
Requirements
Research Findings
 PMT tank material make-up:
 Carbon steel<400 series <300 series SS (corrosive
resistance from lowest to highest)
 Hence the need for a good coating material
 PA PUC Inspection and Maintenance (I&M ) standard 52. Pa Code
 Stages of corrosion
 Curing PMT tanks for successful re-coating application
 1984 Wisconsin Electric Power Company PMT Maintenance Report
 IEEE/ANSI Standards for PMT integrity tests
Pre-surface
inspection
• Hand
blasting
• Clean panels
for dust, oil,
and other
contaminants.
Compatibility
Test
• Paint
Surface
adhesion
Preparation
• Per
IEEE/ASTM
standards
Laboratory
Experiment
Future Work
• Design procedure outline for future students
• Future students could perform actual laboratory experiment for each
coatings and collect and analyze results.
Acknowledgement(s):
•
•
•
•
Mentor, Mr. Michael Dicks of PPL EU
Subject Matter Specialist, Ms. Alexandra Owensby of PPL EU
Mr. George Combs of Utility Restoration
Prof. Martha Dodge, ESEI, Lehigh University