Fann corrosion coupons are made of Cold Drawn seamless mechanical tubing from type 4130 machine-finish steel. The placement of corrosion test rings in the drill string is one of the more common techniques used to evaluate the corrosiveness of drilling-fluid environments on the drill string and other steel equipment.

Removal and examination of these rings after a period of exposure down-hole can be highly informative as to the corrosiveness of the drilling fluid, as well as to the type of corrosion encountered. An examination of scales and pits on the exposed rings gives clues as to the cause of the corrosion, thus aiding in choosing proper remedial action.




C Carbon

.28 - .33

Mn Manganese

.40 - .60

P Phosphorus


S Sulfur


Si Silicon

.15 - .30

Cr Chrome .80 –


Mo Molybdenum

.15 - .25

Ordering Information

Part No.

Drill Pipe Size & Type

Coupon Size

210091 2-7/8 in. Internal Flush and 3-½ in. Slim Hole 2 1/2-in OD x 0.250-in wall
210092 3-1/2 in. Extra Hole and 3-½ in. Full Hole 2 3/4-in OD x 0.188-in wall
210093 3-1/2 in. Internal Flush and 3-½ in. Extra Hole 3-in OD x 0.313-in wall
210094 4 in. Full Hole 3 1/4-in OD x 0.250-in wall
210095 4 in. Internal Flush and 4-1/2 in. Extra Hole 3 3/4-in OD x 0.3125-in wall
210096 4-1/2 in. Full Hole, 
4-1/2 in. Extra Hole, 
4 in. Internal Flush
3 5/8-in OD x 0.375-in wall
210097 4-1/2 in. Internal Flush
5 in. Extra Hole
4 1/2-in OD x 0.3125-in wall
210098 5-9/16 in., 5-1/2 in. API Regular or Full Hole and 6-5/8 in. API Regular 4 5/8-in OD x 0.500-in wall
210099 6-5/8 in. Full Hole K= 202 4 11/16-in OD x 0.282-in wall
210100 4-1/2 in. Extra Hole 3 13/16-in OD x 0.200-in wall
210101 6-5/8 in. Full Hole K= 123.3 5 3/4-in OD x 0.375-in wall
210102 5 in. x H Tool Joint 4 3/16-in OD x 0.2185-in wall

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