Heat Induction Stripping of Thick Film Protective Coatings

Last Updated 2 months ago by Kenya Engineer

Introduction

Protective coatings applied to steel structures eventually reach the end of their service life and must be removed before recoating can take place. Traditionally, abrasive blast cleaning—dry, wet, or vapour—has been the most widely accepted and effective method of coating removal for maintenance painting. However, increasing regulatory controls, environmental concerns, and rising waste disposal costs have driven the industry to explore alternative surface preparation technologies.

One such technology is induction heat stripping, an innovative method that uses controlled electromagnetic induction to rapidly heat steel substrates, breaking the bond between the coating and the steel without the use of abrasive media. This article reviews the practical application of induction heat stripping, examines adhesion performance of coatings applied over heat-stripped surfaces, and discusses where this technology fits within modern maintenance strategies. 

Limitations of Conventional Abrasive Blasting

While abrasive blasting remains effective, it presents several challenges, particularly for in-situ maintenance work:

• Large volumes of abrasive media are consumed.
• Spent abrasive and removed coatings must be collected and disposed of.
• When coatings contain hazardous materials such as lead, chromates, or coal tar, disposal must be carried out at licensed facilities, significantly increasing project costs.
• Enclosures, scaffolding, and dust containment measures are often required, further escalating costs and limiting access.

Alternative methods such as water jetting and wet or vapour blasting reduce airborne dust but introduce other constraints, including residual abrasive waste, water management issues, and restrictions around electrical installations.  

Emergence of Induction Heat Stripping

In 2019, an Australian industrial coating contractor introduced the RPR 1032 induction heat paint removal system, marking the first commercial use of this technology in Australia. The system was acquired to assess whether induction heat stripping could, in specific applications, replace abrasive blasting or significantly reduce its scope.

The key drivers for adoption included:

• Reduced waste generation
• Elimination of abrasive media
• Suitability for sensitive environments and over-water work
• Improved control when removing hazardous coatings

The technology works by heating the steel substrate rather than the coating itself. As the steel expands, the coating loses adhesion and can be mechanically lifted away, leaving the original surface profile largely intact. 

Observing the Stripping Process

To better understand the impact of induction stripping on coating performance, the contractor invited their principal coating supplier to observe and document the process. Test panels were initially abrasive blast cleaned to Sa 2½, coated with various industrial coating systems (including thick-film epoxies and rubber linings), and then allowed to fully cure.

Following induction heat stripping, it was observed that:

• The majority of the coating was cleanly removed.
• Small residues remained in the valleys of the original blast profile.
• No abrasive contamination was introduced to the surface.

This raised a critical question: Can modern surface-tolerant coatings achieve adequate adhesion over induction-stripped steel surfaces? 

Adhesion Testing: Initial Findings (2019)

To investigate this, heat-stripped panels were recoated using aerosol-packaged two-component epoxy and polyurethane products. These products contained the same formulations as their conventionally packaged equivalents and were applied without further surface preparation beyond removal of loose residues.

Pull-off adhesion testing, conducted in accordance with ISO 4624, demonstrated adhesion values well in excess of commonly accepted minimum requirements. These results indicated that surface-tolerant epoxy coatings could bond effectively to induction-stripped surfaces, even where minor residues remained.  

Expanded Testing Program (2023)

Further testing was conducted in 2023 to include conventionally packaged coatings and a wider range of systems. Six panels were prepared with commonly used industrial coating systems, heat stripped after full cure, and then recoated.

Adhesion testing was performed using:

• ISO 4624 methodology
• Six tests per panel
• Araldite Standard adhesive
• Dry film thickness verification in accordance with SSPC-PA 2

The coatings tested included:

• Surface tolerant epoxies
• High solids immersion-grade epoxies
• High build epoxies
• High temperature epoxies

Across all tested systems, adhesion values significantly exceeded the 5 MPa minimum referenced in NORSOK M-501, providing further confidence in the viability of induction heat stripping as a surface preparation method. 

Practical Applications and Limitations

Based on the test results and field experience, the contractor has adopted induction heat stripping for applications where conventional abrasive blasting is impractical or restricted, including:

• Bulk storage tanks
• Wharf and marine infrastructure
• Large-diameter pipelines
• Lead paint removal projects
• Heritage and sensitive structures

Where possible, light abrasive brush blasting (SSPC-SP 7) is still used after stripping to remove residual coating from profile valleys and restore visual cleanliness. However, for small or inaccessible areas, coatings have been successfully applied directly over heat-stripped surfaces using surface-tolerant systems.

To date, the technology has been used on more than 55,000 m² of steel structures in Australia, with international usage exceeding 350,000 m². 

Conclusions

Induction heat stripping offers a credible and effective alternative to conventional abrasive blasting in specific maintenance scenarios. Adhesion testing conducted in both 2019 and 2023 demonstrates that modern epoxy coating systems can achieve excellent adhesion over heat-stripped surfaces when applied correctly.

While adhesion performance is encouraging, coating selection must still consider environmental exposure, system build-up, and service conditions. Induction heat stripping should be viewed as a complementary surface preparation method rather than a universal replacement for abrasive blasting.

Geoffrey White has over 45 years’ experience in the surface coatings industry. He is a Project Manager with extensive expertise in coating specifications, surface preparation techniques, and field application of protective coatings across industrial and marine environments.

Geoff is an AMPP Senior Coating Inspector, AMPP Protective Coating Specialist, Level 3 FROSIO Coating Inspector (retired), and a Certified Corrosion Technologist with the Australasian Corrosion Association (ACA), of which he is a Life Member. He currently works with International Paint (AkzoNobel) as a Technical Specialist in Protective and Marine Coatings.