Corrosion Rings-I

Corrosion rings are sized to fit in the relief groove in the tool joint box in the drill string. Corrosion coupons are
typically used in aging cells in a laboratory environment, or at select locations within the flow line. Both are
exposed to fluid for a period of time and the difference between the initial and the final weights (or the weight
loss) is attributed to corrosion. The corrosion rate is calculated and reported as lb./ft2/yr., or mils per year (my).
The term "mils per year" refers to the loss of metal in thousandths of an inch per year.
lb.ft2/year = Weight loss, grams
Exposure time, hours
(Weight Loss, grams) (1000)
Sp. gravity x 16.387 x area x year
(ml/in3) (in2) (days/365)
Note: The K factor is the constant used for the area of the ring that is exposed and the metal density of
that ring.
mils per year = lb/ft2/year x 24.6
A corrosion rate of 2 lbs/ft2/year or 50 mpy is a reasonable criteria for corrosion rate but this may vary
with individual conditons.
For more information, please contact us:
10700 Rockley Road
Houston, Texas 77099
281-496-0900 [voice]
281-496-0400 [fax]
E-mail: [email protected]