scope:

This standard is presented for the use of corrosion coupons in oilfield drilling, production, and transportation operations. Oilfield operations include oil-, water-, and gas-handling systems, and drilling fluids. (When used in this standard, system denotes a functional unit such as a producing well; flowline and tank battery; water, oil, or gas collection facility; water or gas injection facility; or a gas dehydration or sweetening unit.) Corrosion coupon testing consists of the exposure of a small specimen of metal (the coupon) to an environment of interest for a period of time to determine the reaction of the metal to the environment. Corrosion coupons are used to eval- uate corrosiveness of various systems, to monitor the effectiveness of corrosion-mitigation programs, and to evaluate the suitability of different metals for specific systems and environments. The coupons may be installed in the system itself or in a special test loop or apparatus. Corrosion rates shown by coupons and most other corrosion-monitoring devices seldom duplicate the actual rate of corrosion on the system piping and vessels. Accurate system corrosion rates can be determined by nondestructive measurement met hods or failure fre- quency curves. Data furnished by corrosion coupons and other types of monitors must be related to system requirements. High corrosion rates on coupons may be used to verify the need for corrective action. If a corrosion-mitigation program is initiated and subsequent coupon data indicate that corrosion has been reduced, the information can be used to approximate the effectiveness of the mitigation program. This standard does not contain information on monitoring for inter- granular corrosion, stress corrosion cracking (SCC), or sulfide stress crackin (SSC). The latter aspects are discussed elsewhere. (footnote 1),(footnote 2)

This standard describes preparation and handling techniques for metal coupons prior to and following exposure. Corrosion rate calculations and a typical form for recording data are also included.

Footnote 1 - NACE Standard MR0175 (latest revision), ¿Sulfide Stress Cracking Resistant Metallic Materiais for Oilfield Equipment,¿ (Houston, TX: NACE International).

Footnote 2 - E.M. Moore, J.J. Warga, ¿Factors Influencing the Hydrogen Cracking Sensitivity of Pipeline Steels,¿ CORROSION/76, paper no. 144 (Houston, TX: NACE, 1976).