Petrochemical Facility

Extreme Performance in Extreme Environments

Reprinted from

Materials Performance An Official NACE International Publication
Volume 37 • Number 4

Fluoroelastomers Show High Resistance in Surface Applications

Fluoroelastomers are fluorine-containing synthetic rubbers that are commonly used in the molding and extrusion of O-rings, seals and similar sealing products for the automotive and aerospace industries. Because of their resistance to temperature extremes and many chemicals and corrosive liquids, the materials are increasingly used as coatings, adhesives, sealants, and caulking compounds for use in aggressive environments.

Dave Bender of Bender Engineering (Ontario, Canada) found that fluoroelastomers offered high resistance when exposed to such potent chemicals as 98% sulfuric acid (H₂SO₄), 85% phosphoric acid (H₃PO₄), 4% nitric acid (HNO₃), concentrated sodium hydroxide (NaHO), and potassium hydroxide (KOH). He has used the materials to solve severe corrosion problems in several chemical and dairy applications.

One project involved the secondary containment of an H₂SO₄ storage area at a petrochemical refinery. The acid was stored in two 20' high by 8' wide tanks, each of which was mounted on a set of four piers. Each set of piers was mounted in the center of an 11' by 12' concrete pad located within the 300 square foot containment area. Upon inspection, Bender noted cracks about 1/8" wide on the concrete floors, evidence that the pads were corroding because of a coating failure.

Resistance of Elastomers Exposed to Acid (Pelseal Technologies Laboratory Tests)

Cured samples of four elastomeric caulking materials were tested to measure their resistance to acids. Acid immersions were performed for 7 days at room temperature. Volume swell was measured per ASTM D-471 (A) and recorded as a percentage. It was not possible to qualify the volume change for samples that dissolved.

Fluoroelastomer	Silicone	Polyurethane	Polysulfide
HNO3 70% vol -21.4%	Dissolved after 5 hours	Dissolved after 3 hours	Reacted violently, dissolved immediately
H2SO4 98% vol -11.3%	Dissolved after 30 min	Dissolved after 20 minutes	Dissolved after 20 min
(A) ASTM D-471, "Standard Test Method for Rubber Property-Effect of Liquids," (West Conshohocken, PA: ASTM)

After resurfacing the concrete with epoxy surfacer and epoxy novalac topping, the cracks were recut and filled with backer rod, a lightweight polyethylene material. To complete the job, the cracks were sealed with a liquid fluoroelastomer caulk that had the chemical and heat resistant properties to withstand the highly corrosive effects of H₂SO₄. Manufactured by Pelseal Technologies, LLC, Pelseal PG had undergone laboratory and field tests showing that it could withstand temperatures ranging from -40° F to 400° F (-40° to 204°C) and resist attack by more than 300 chemicals and corrosive liquids.

Bender has since used liquid fluoroelastomers to solve corrosion problems in the water treatment area of a petrochemical refinery plant, and in five dairy processing plants that suffered floor corrosion from HNO₃, H₂SO₄, H₃PO₄, and other chemicals used for sanitation and cleaning.