Tanks, pipes and scrubbers made of carbon or stainless steel will corrode sooner or later when they handle acids or oxidizing media. An ECTFE coating keeps the medium away from the metal altogether. A fluoropolymer coating can still fail, though, when material selection, surface preparation or inspection fall short. Repairs and downtime then quickly cost more than the protection itself. This article explains when a protective layer of ECTFE is the right choice, how it is applied and which factors decide its service life.
Corrosion is rarely just a materials issue. In petrochemical and chemical plants, an attacked tank wall or pipe leads directly to:
Many installations rely on epoxy or rubber linings, and for plenty of applications that is enough. With oxidizing media such as chlorine or hypochlorite, or at elevated temperatures, these systems fall short: they harden, blister or let the medium through.
The damage usually becomes visible only once the metal underneath has already been attacked. What follows is a full refurbishment, including downtime.
ECTFE (ethylene chlorotrifluoroethylene) combines several properties that matter most for corrosion protection:
So where is the bottleneck? Rarely in the material. A corrosion-resistant coating is only as good as its weakest spot: an insufficiently blasted surface, a layer that is too thin, or a single pinhole. Through that pinhole, the medium still reaches the metal. The low permeation of the rest of the layer no longer helps.
Weighing ECTFE against other fluoropolymers? Our article on ECTFE vs ETFE covers that choice.
An ECTFE coating, often called a Halar® ECTFE coating, is usually applied as an ECTFE powder coating. The process has three phases:
For large or heavily loaded equipment, an ECTFE lining is an alternative: ECTFE sheet installed on the substrate and welded at the seams. Typical applications for ECTFE coatings and linings:
Record which media the coating will see, at what concentration and temperature, including peaks during cleaning cycles. Also note mechanical loads such as abrasion, agitation or vibration.
A coating follows complex shapes accurately and suits parts that fit in an oven. A sheet lining provides a thicker barrier and suits large tanks. If the media are less aggressive, also consider PVDF as a coating material.
Put the blasting grade and minimum layer thickness in your specification. Thickness typically ranges from a few tenths of a millimeter to about 1 mm, depending on the application.
Check the chemical resistance of ECTFE for all your media beforehand. When you compare ECTFE coating services, ask each applicator how they document these values.
Require a high-voltage spark test over the entire surface. This finds pinholes before commissioning, not after corrosion appears.
Set an inspection interval and focus on edges, welds and mechanically loaded zones. Repairing small damage early prevents major repairs later.
A familiar scenario: a steel storage tank for sodium hypochlorite in a chemical plant has an epoxy coating. After a few years, blisters and rust spots appear. The oxidizing medium has attacked the coating.
For the refurbishment, ECTFE is a logical choice: resistant to oxidizers and with very low permeation. The critical points then shift to execution: thorough blasting, sufficient thickness and a spark test before the tank returns to service.
ECTFE protects carbon and stainless steel where epoxy and rubber fall short: with acids, oxidizers and temperatures up to 150 °C. Its very low permeation prevents underfilm corrosion. The material is only half the story, though. Surface preparation, layer thickness and freedom from pinholes determine service life. Specify those three upfront, and corrosion protection will not become a maintenance item of its own.
Want to know whether an ECTFE coating suits your installation? Our specialists are happy to think along with you about material and execution. Contact us for free expert advice.
Halar® is a brand name of Syensqo (formerly Solvay) for ECTFE. A Halar ECTFE coating is therefore an ECTFE coating: a fluoropolymer layer, usually applied as a powder coating, that protects metal against acids and oxidizing media. Performance depends on the application and layer thickness, not on the brand name.
Typically from a few tenths of a millimeter to about 1 mm, depending on the medium and the load. The layer is built up in several coats. Always specify the minimum thickness.
ECTFE can be used continuously from −75 °C to +150 °C and short-term up to 180 °C. In combination with aggressive media, the practical limit may be lower. Have this assessed for your application.
A coating is a fused powder layer: thin, seamless and suited to complex shapes. A lining consists of ECTFE sheets that are installed and welded at the seams. A lining is thicker and is mainly used in large tanks and vessels.
Ask how the applicator prepares the surface, which layer thickness they guarantee and whether a spark test over the full surface is standard. Also check that the material choice has been tested against your actual media and temperatures. These three points largely determine the service life of the coating.