LEADERS in CORROSION CONTROL

Allied Corrosion Industries, Inc.

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Stress Corrosion Cracking Direct Assessment (SCCDA)

What is Stress Corrosion Cracking?

Stress Corrosion Cracking Direct Assessment (SSCDA): As defined in the NACE Standard RP0204-2004, Stress Corrosion Cracking (SCC) is the cracking of material produced by the combined action of corrosion and tensile stress (residual or applied). SCCDA Methodology is a procedure that can identify areas where either near-neutral-pH SCC or high-pH SCC can occur on external pipe surfaces. The SCCDA process consists of four steps:

Causes

Stress Corrosion Cracking can be caused by combined corrosion and tensile stress, which can include cold deformation and forming, welding, heat treatment, machining and grinding.

The SCCDA Process

1. Pre-Assessment

In the pre-assessment step, Allied Corrosion or the owner/operator's personnel will collect historical and current data for the purposes of analyzing and prioritizing the threat of Stress Corrosion Cracking. Prioritization of SCC susceptible pipeline segments is performed utilizing the following factors:

High-pH Stress Corrosion Cracking

  • Operating stress exceeds 60% of SMYS
  • Operating temperature exceeds 100°F (38°C)
  • Within 20 miles of a compressor station
  • Age greater than or equal to 10 years
  • Coating type other than Fusion Bonded Epoxy

Near Neutral-pH Stress Corrosion Cracking

  • Operating stress exceeds 60% of SMYS
  • Within 20 miles of a compressor station
  • Age greater than or equal to 10 years
  • Coating type other than Fusion Bonded Epoxy

2. Indirect Inspection

The purpose of the indirect inspection step is to collect additional information that was not available in the owner/operator's historical records. Some of the data that Allied could collect in this step would include data from Close Interval Surveys (CIS), Direct Current Voltage Gradient (DCVG) surveys, and terrain conditions (soil type, topography, and drainage) along the right-of-way (ROW) in which the pipeline is located. Once all of this information is assembled, the direct examination site list is finalized and prioritized.

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3. Direct Examination

The purpose of the Direct Examination step is twofold. First, this step will either validate or nullify the decision criteria for SCC direct examination site selection. Second, this step provides for the actual digging of the suspected SCC locations for inspection. When performed, these dig sites will render the severity, extent, and type of SCC (intergranular or transgranular cracking). This information is crucial in the post assessment process in order to develop a predictive model and allow for modifications. A wide range of related physical data is collected, along with Magnetic Particle Inspection (MPI) of the susceptible area. NACE Standard RP0204-2004 outlines four different MPI techniques for inspecting the external surface of pipelines. They are:

 

  • DPMI- Dry Powder MPI: The ultimate sensitivity of this inspection technique is 2 to 5 mm long defects.
  • WFMPI- Wet Fluorescent MPI: The ultimate sensitivity of this inspection technique is 1 mm long defects.
  • WVMPI- Wet Visual MPI: The ultimate sensitivity of this inspection technique is 1 to 2 mm long defects.
  • BWMPI- Black on White MPI: The ultimate sensitivity of this inspection technique is 1 to 2 mm long defects. This technique is preferred over the other due to the ease of photographic documentation and maintaining a high sensitivity.

 

 

 

 

 

4. Post Assessment

In the post assessment step, Allied Corrosion or the owner/operator will analyze the data collected from the previous three SCCDA steps for the following purposes:

  • To determine if stress corrosion cracking mitigation is required and if so, prioritize those actions.
  • To define the time interval to re-assess the pipeline segment.
  • To evaluate and verify the decision model used to find stress corrosion cracking.

Our Integrity Management Team is ready to provide turn-key SCCDA services or we can perform any single or multiple step(s) that you, the owner/operator require.

The Allied Corrosion Difference

Our strong understanding of the potential destruction from a compromised pipeline allows us to deliver detailed Stress Corrosion Cracking Direct Assessment to complement any operator's Integrity Management program. Our comprehensive pipeline integrity and cathodic protection engineering services will keep your pipeline assets protected throughout its life-cycle.

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NEED A CORROSION EXPERT?

Contact Allied Corrosion Today

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1550 Cobb Industrial Dr.  |  P.O. Box 9098  |  Marietta, GA 30065-2098

770-425-1355 (Phone) | 770-425-1354 (Fax) | info@alliedcorrosion.com (Email)

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Material
Voltage Range
Relative Position
Least Noble (More Anodic)
Magnesium
-1.60V to -1.67V
Zinc
-1.00V to -1.07V
Beryllium
-0.93V to -0.98V
Aluminum Alloys
-0.76V to -0.99V
Cadmium
-0.66V to -0.71V
Mild Steel
-0.58V to -0.71V
Cast Iron
-0.58V to -0.71
Low Alloy Steel
-0.56V to -0.64V
Austenitic Cast Iron
-0.41V to -0.54V
Aluminum Bronze
-0.31V to -0.42V
Brass (Naval, Yellow, Red)
-0.31V to -0.40V
Tin
-0.31V to -0.34V
Copper
-0.31V to -0.40V
50/50 Lead/Time Solder
-0.29V to -0.37V
Admiralty Brass
-0.24V to -0.37V
Aluminum Brass
-0.24V to -0.37V
Manganese Bronze
-0.24V to -0.34V
Silicon Bronze
-0.24V to -0.30V
Stainless Steel (410, 416)
-0.24V to -0.37V
(-0.45V to -0.57V)
Nickel Silver
-0.24V to -0.30V
90/10 Copper/Nickel
-0.19V to -0.27V
80/20 Copper/Nickel
-0.19V to -0.24V
Stainless Steel (430)
-0.20V to -0.30V
(-0.45V to -0.57V)
Lead
-0.17V to -0.27V
70/30 Copper Nickel
-0.14V to -0.25V
Nickel Aluminum Bronze
-0.12V to -0.25V
Nickel Chromium Alloy 600
-0.09V to -0.15V
(-0.35V to -0.48V)
Nickel 200
-0.09V to -0.20V
Silver
-0.09V to -0.15V
Stainless Steel (302, 304, 321, 347)
-0.05V to -0.13V
(-0.45V to -0.57V)
Nickel Copper Alloys (400, K500)
-0.02V to -0.13V
Stainless Steel (316, 317)
0.00V to -0.10V
(-0.35V to -0.45V)
Alloy 20 Stainless Steel
0.04V to -0.12V
Nickel Iron Chromium Alloy 825
0.04V to -0.10V
Titanium
0.04V to -0.12V
Gold
0.20V to 0.07V
Platinum
0.20V to 0.07V
Graphite
0.36V to 0.19V
Most Noble (More Cathodic)

Primary voltage range for material
Voltage range in crevices or stagnant and poorly aerated water