corrosion coupons

CLIMAT coupons for atmospheric corrosion monitoring and crevice corrosion coupon

Corrosion Coupons:

Corrosion coupons represent a widely used ("traditional") and relatively simple form of corrosion monitoring. Usually a coupon is exposed to a corrosive environment to represent an actual component/structure. Subsequent to their exposure, coupons can be weighed and examined microscopically to assess the mode and average rate of corrosion damage. This form of corrosion monitoring is therefore usually of a retrospective nature - only a snapshot of the cumulative corrosion damage at the end of the exposure period is provided and little information is available on specific events that may have triggered this damage.

Much interest is currently focused on the use of corrosion coupons for monitoring the performance of CP systems on buried pipelines. In these applications, the coupons represent simulated pipeline coating defects. The potentials and CP current flow on the coupons can be monitored as performance indicators of the CP systems.

Even though this monitoring technique is relatively simple, mistakes can easily be made that can render poor quality (or even meaningless) coupon corrosion data. Attention to detail cannot be overemphasized, especially when the coupons have to be made representative of actual components/structures.

References/Literature:

ASTM G4 Standard, "Conducting Corrosion Coupon Tests in Plant Equipment," American Society for Testing and Materials, West Conshohocken, PA.

K.M. Lawson and N.G. Thompson: "The Use of Coupons for Monitoring the Cathodic Protection of Buried Structures", Paper # 672, Corrosion 98, NACE International, San Diego, 1998.

T.J. Barlo: "Cathodic Protection Parameters Measured on Corrosion Coupons and Pipes Buried in the Field", Paper # 661, Corrosion 98, NACE International, San Diego, 1998.

J.L. Didas: "The Use of IR Drop Coupons as a Practical & Effective Test Method", Paper # 666, Corrosion 98, NACE International, San Diego, 1998.

Links:

Information provided by Metal Samples, a commercial supplier:
http://www.alspi.com/msc.htm

which also features a technical article by Bert Krisher: www.alspi.com/cpntst.htm

Information on CLIMAT atmospheric corrosion monitoring coupons from Corrosion Doctors:
www.corrosion-doctors.org/AtmCorros/Frames.htm

Article on corrosion coupons (pdf file) submitted to corrosion-club.com by Mr. Bill Duncan of CorrView:
"The Benefits and Limitations of Corrosion Coupons" by B. Duncan.