BAKER HUGHES - Drilling Fluids Reference Manual

CORROSION
6. After the run, carefully remove the ring coupon, preventing any mechanical damage that
could cause a weight loss.
7. Immediately upon its removal from the string, wash off any excess fluid and fluid solids
adhering to the ring coupon. Wipe dry and apply a light coat of grease or heavy oil to the
ring coupon to protect it from atmospheric corrosion. Do not use pipe dope.
8. Rewrap the ring coupon and record on the shipping envelope the requested information.
Be sure to record the date and time the ring coupon was installed and removed as well as
the fluid type and any corrosion control techniques and treatments in effect during the ring
coupon run. Ship the ring coupon to the processing lab as soon as possible.
Calculation of Corrosion Rate
The corrosion rate, based on weight loss (from corrosion coupon analysis), is calculated as follows.
Corrosion Rate,
lb
m
/
ft
2
/ yr =
( K )( Weight Loss,
gm)
ExposureTime,
hr
2
Mils / yr = lb / ft / yr × 24.6
m
Where:
K = a constant used for the area of the ring coupon exposed and is printed on the shipping
envelope.
Note:
Constants for plastic coated rings are significantly different and should not be
interchanged.
CORROSION TREATMENT TIPS
Oxygen Scavengers
NOXYGEN
NOXYGEN is a liquid and is packaged in 55 gal drums. Best application is by chemical
injection pump into the suction line. Initial injection rate should be as high as the pump will allow,
reducing the rate as necessary to obtain the required sulfite residual at the flowline. Maintain 75 to
125 mg/L sulfite residual. Large diameter boreholes with high circulation rates will require higher
chemical injection rates. All fittings and valves on the chemical injection equipment should be of
good quality stainless steel. All fittings should be air tight. Avoid copper and brass fittings.
BAKER HUGHES DRILLING FLUIDS
REVISION 2006 8-10
REFERENCE MANUAL