Materials Selection – Non Metals PTRT 1309 Corrosion Basics Chapter 5 – NACE Book Materials Selection – Non Metals Prepared by Dr. Capone

Non metallic Materials Generally refers to plastic or fiber-reinforced plastics (FRP) Also refers to Wood Concrete Cement Mortar Cement asbestos tile

Wood Excellent corrosion resistance (fasteners) Not generally used today Expensive to construct, install and maintain Coated steel tanks now generally superior economically

Cement and Concrete Reinforced offshore structures Foundations for equipment Linings for tank bottoms, internal pipe coatings, secondary containment basins Generally resistant to corrosion except for reinforcing materials Alkaline cement forms passive layer on reinforcing materials which if damaged can cause corrosion to occur Generally caused by chlorides or oxygen Corrosion of rebar generally leads to cracking and/or spalling of the concrete

Minimizing Corrosion in Concrete Least permeable composition of concrete Low in contaminants Several inches between outside and rebar Fusion bonded epoxy (FBE) Coatings (powder coating) Alkalization and/or realkalization Cathodic protection Surface coatings (stop penetration of environment into concrete)

Rebar in gelatin with chloride Rebar in gelatin with chloride and nitrite.

Cement-Asbestos Used until the early 1970’s Homogeneous mixture of Portland Cement, Asbestos fibers and Silica No longer allowed due to serious health risks Caution must be taken when exposed to this material on older sites (licensed abatement company required)

Transite pipe (cement-asbestos)

Plastic (Polymeric) Materials Most widely used non-metallic materials in the oil field Most under-used corrosion control option Mostly due to misapplication of the products as a direct replacement for steel Various properties must be factored into decision to use plastics Thermal expansion (high) Long-term creep Temperature limitations Chemical resistance Exposure to UV

Plastic (Polymeric) Materials Using modern design information plastics are quite acceptable for a variety of oilfield applications Downhole tubing Flowlines Facility piping Tanks Internal components for water handling vessels Many plastics available with different physical, chemical and mechanical properties

Plastic (Polymeric) Materials Plastic = nonmetallic compound usually synthesized from organic compounds through polymerization (linking of complex molecules) Generally fall into two broad categories Thermoplastic materials Can be melted or reformed with little or no change to their properties Lower temperature limits yield less severe service environments Styrene, PVC, polyethylene, etc Thermosetting materials These plastics are “cross-linked” and do NOT melt Higher temperature limits Epoxy, polyester

Thermoplastics Common thermoplastics Polyvinyl chloride (PVC) Polyethylene (PE) Low-density PE (LDPE) High-density PE (HDPE) Polyproplyene (PP) Used for low-pressure piping, pipe liners, chemical storage drums Fabrication is similar for all Pelletized feed stock is melted Extruded or injection molded into finish forms Cooled and thus rehardened

Thermosetting Plastics Usually known as FRP – Fiber Reinforced Plastic Falls into general class of materials called composites Fiberglass Carbon-fiber Other fibers Generally resin (epoxy or polyester) in impregnated with fiber mats

Also examine figures on page 89 in large textbook

Fiber reinforced pipe Generally manufactured by Filament winding Centrifugal casting Glass or ceramic fibers are saturated with resin (epoxy or polyester) Correct resin selection for specific applications is critical

Joining Methods Heat Welding Solvent Welding Threaded connections Heating element (sometimes IR) used to soften the joints Compressed and fuse together (upset can occur) Solvent Welding Chemical solvent softens the plastic which then fuses (often called gluing) Threaded connections Schedule 80 usually specified for threaded joints Working pressure usually reduced by 50%

Application of Non-metallic pipe Three important factors Chemical resistance Mechanical properties Economics Usually the primary concern Most materials discussed in this chapter are resistance to oil field fluids Some absorption can occur which causes weakening Service or environmental factors must be considered See Table 5.2, page 91 Mechanical Properties Pressure and Temperature Ratings Surging can be 10x – 15x the average pressure in the line

Typical Applications Thermoplastics FRP Flow lines – between well head, separators, tank battery Gathering lines – oil, water or low pressure gas Salt water lines – disposal systems and drains Liners – for steel pipe in high pressure applications Fuel lines – for gas engines FRP Used for all of the above Tubing for injection and disposal wells

Advantages and Disadvantages Immune to corrosion by water Lightweight = lower freight and handling costs Quickly and easily joined and installed No external corrosion protection required Smooth internal surface yields lower friction losses Disadvantages Limited working temperature and pressure Limits are difficult to predict Careful handling is required Must be protected from sunlight, freezing, fire Weeping can occur in low quality FRP Low resistance to vibration and surging

FRP Tanks Most numerous are the small oilfield chemical tanks Inner layers designed to protect against chemical attack and are typically structural Outer layers designed to prevent atmospheric absorption and UV degradation See Table 5.2, page 91 FRP sucker rods – still have metal connections

Elastomers Common uses as seals and packing Also used in tank liners Most common seals are: Nitrile (Buna-N) EPDM (ehtylene-propylene-dienemonomer) Flourocarbon HSN (Highly Saturated Nitrile)

Selection of Seals