Non-Magnetic Drill Collars

Pitting Corrosion Test Procedure

The test specimen is tested in a test cell at a controlled temperature (20°C/68°F) and in a test solution of chlorides (e.g. 1000 ppm CI). The test temperature and the chloride content of the test solution are principally variable.

The measurement of the Pitting Corrosion Potential of the specimen is carried out against a reference electrode (Kalomel-Electrode). The steady increase in the applied potential is regulated by a motor potentiometer. The amount of increase of the potential is given with 150 mV/hr (comparable ASTM G5/87: 720mV/hr)

The Potential at which first a deviation from a constant current level can be examined is stated as the "Pitting Corrosion Potential".



Stress Corrosion Resistance

All SB Darron Non-magnetic materials basically show a very good resistance against stress corrosion. For the application of these materials in high chloride muds a surface treatment as an additional protection against stress corrosion is strongly recommended.

SB Darron provides following special processes to apply a uniform compressive surface layer:
 

• Hammer Peening
• Roller Burnishing
• Shot Peening

Tests carried out on each bar during production of drill collars & MWD-Parts
 

• Tensile Test
• Impact Test
• Hardness Test
• Metallographic Test (grain size)
• Oxalic Acid Test (acc. To ASTM A262 – Pract.E)
• Ultrasonic Test over whole length of the bar
• Probe Test over whole length of the bar

Tests carried out on each melt
 

• Chemical Analysis Relative Magnetic Permeability

Standard Certification Package
 

• Certification Sheet
• Ultrasonic Report
• Probe Testing Report

Additional reports based on product (mainly for MWD / LWD – Parts) 
 

• Dimensional Report
• Surface Treatment Report
• Welding Report

Magnetic Properties
 

• Relative Permeability : ≤1.001

Corrosion Resistance
 

• Transgranular SCC 

 

• Intergranular SCC 

Non-Destructive Testing
 

• Magnetic Inspection

 

• Ultrasonic Inspection