Internal Corrosion Chapters 1 - 7

Question 1

What is the Corrosion Investigator’s first job on-site?

Answer 1

Protect all evidence

Question 2

What is the Corrosion Investigator’s second job on-site?

Answer 2

Collect all evidence

Question 3

How can the presence of water be confirmed in a sample?

Answer 3

By using Hydrion paper

Question 4

Which gas analysis test CANNOT be collected with a stain tube?

Answer 4

Pressure

Question 5

What is the procedure that penetrates and preserves the scale, corrosion product, microbes, and deposits that are present on an internally corroded pipe?

Answer 5

Embedment

Question 6

What two common devices are used to measure the temperature of liquid samples in the field?

Answer 6

1) A clean thermometer, and 2) An electronic temperature probe.

Question 7

These samples must be taken where there are differences in color, texture, density or composition of materials in the pipe. These samples must be taken carefully to avoid damaging other corrosion evidence and must be carefully identified in terms of physical location.

Answer 7

Solid / sludge sampling.

Question 8

The pH of aqueous samples is measured with what two common methods?

Answer 8

1) pH paper, and 2) pH meter.

Question 9

These samples are normally collected in stainless steel sample bottles or Tedlar bags. Stain tubes can sometimes be used to replace some samplings.

Answer 9

Gas sampling.

Question 10

With this method, you collect at least 500 ml in two 250 ml sample containers at the site of the cut if possible. Samples should be filled to the top to exclude air and capped. Samples should be kept in a cool dark place if possible.

Answer 10

Liquid sampling.

Question 11

This method provides elemental compositional analysis of very thin (3mm) surface layers. It has better spatial resolution and sensitivity and is more quantitative than EDS. It is only appropriate for certain types of corrosion related samples such as selective corrosion at grain boundaries or other metallurgical features.

Answer 11

AES (Auger Electron Spectroscopy).

Question 12

These two methods are used with microscopes to examine small areas or features. Both methods usually allow mapping of the surface and are used for bulk sample analysis.

Answer 12

FTIR (Fourier Transform Infrared) and Raman Spectroscopy

Question 13

This is a common technique used to identify crystalline phases in unknown materials. These crystalline phases are described as compounds rather than elements which is beneficial in understanding corrosion reactions. It requires only a few grams of sample and non-crystalline components can also be identified.

Answer 13

XRD (X-Ray Diffraction)

Question 14

A long established technique used to identify nearly 70 different elements in liquid and solid samples down to parts per billion. This technique is used to identify metallic elements found in corrosion products that couldn’t be found using ion chromatography.

Answer 14

Atomic Absorption

Question 15

With this method, the sample should be cut using a portable band saw or wheel-type cutter to prevent torch cutting debris from entering the sample. The sample should be marked with relevant operating information such as flow direction, top, bottom, mile post, wheel count, etc.

Answer 15

Pipe sampling.

Question 16

This method is used to look for corrosion inhibitors, biocides, methanol, glycol, and other organic materials but the investigator MUST have some idea of the organic material for which they are searching.

Answer 16

Gas or Liquid Chromatography.

Question 17

These two methods can quantitatively identify over 70 elements in liquids, solids, and particulates. They provide shorter analysis times than AAS. Sample sizes of 100 ml for liquids and 1 gram for solids are common.

Answer 17

DCP / ICP (Direct Current Plasma / Inductively Coupled Plasma)

Question 18

This procedure uses liquid chemistry data to calculate values which are simply indications as to the propensity for deposition or dissolution of calcareious deposits.

Answer 18

Scaling Index.

Question 19

This term describes laboratory analysis techniques such as gravimetry, titrimetry, and numerous separation methods. It is time consuming and the methods vary widely with sample type and composition and often require some educated guesswork to describe a nonhomogeneous sample.

Answer 19

Wet Chemistry.

Question 20

This is a popular method for determining the concentrations of ionic species in aqueous samples. Typical results would identify sulfate, sulfite, nitrate, nitrite, phosphate, chloride, bromide, and fluoride ions. It can also identify the organic acids present in an aqueous sample. Results are reported in either ppm or mg/L.

Answer 20

Ion Chromatography.

Question 21

This pair of tests are some of the most common techniques used for examining and analyzing elemental surface components of corrosion-related samples. One test provides a high-resolution view of the corroded surface and corrosion products while the other provides elemental chemical composition data of both discrete particles and larger areas. This combination analysis is an investigative procedure that the corrosion investigator should directly observe and participate in whenever possible.

Answer 21

SEM / EDS (Scanning Electron Microscopy / Energy Dispersive Spectroscopy)

Question 22

This technique is used more frequently in the study of microorganisms than of corrosion. Histological embedments of corrosion products and biofilms can be used in this process by taking thin sections from the embedment. The primary limitation of this procedure is the length of time required for preparation and the cost.

Answer 22

TEM (Transmission Electron Microscopy)

Question 23

This method is like Auger as another method that analyzes atomic surface layers for elemental compositions. It is more sensitive and has better spatial resolution than EDS. It is sensitive to trace elements in the parts per million and parts per billion range. It can characterize both inorganic and organic surface materials. It is used for compositional depth profiling, bulk impurity analysis, and examination of specific metallurgical features.

Answer 23

SIMS (Secondary Ion Mass Spectroscopy)

Question 24

What is the final and most important part of instituting a corrosion mitigation program?

Answer 24

Monitoring the effectiveness of the treatment.

Question 25

What are the three major methods for mitigating internal corrosion once the cause has been identified?

Answer 25

1) Remove the environment that promotes the corrosion in the first place; 2) Change the internal environment by altering operating & maintenance procedures; and 3) Employ chemical treatment with inhibitors or biocides.

Question 26

What is step #1 in the “Reviewing the Results”?

Answer 26

1: Get organized

Question 27

What is step #2 in the “Reviewing the Results”?

Answer 27

2: Ask the 20 questions and answer them.

Question 28

What is step #3 in the “Reviewing the Results”?

Answer 28

3: Make connections among data produced by the investigation.

Question 29

What is step #4 in the “Reviewing the Results”?

Answer 29

4: Tell a story - a factual story of what happened to cause the corrosion found.

Question 30

What is step #5 in the “Reviewing the Results”?

Answer 30

Put it into writing.

Question 31

Who should develop an investigative plan for an internal pipeline corrosion failure?

Answer 31

A team.

Question 32

Which visual appearance may indicate the effects of historical liquid levels in the pipeline?

Answer 32

Corrosion in longitudinal bands along both sides of the pipe.

Question 33

Which internal pipeline condition most indicates hydrogen sulfide presence?

Answer 33

Odor similar to rotten eggs.

Question 34

When collecting physical evidence of internal corrosion, cleaned pipe should be used primarily for what?

Answer 34

Dimensional analysis.

Question 35

Which type of physical evidence is intended to capture the deposits and biofilm and their relation to the corrosion?

Answer 35

Nodules.

Question 36

Concentration cell corrosion within small areas isolated from the bulk fluid stream.

Answer 36

Crevice corrosion at joints.

Question 37

General etching over large continuous areas that still contain isolated pitting or cluster of pits.

Answer 37

Isolated pitting within General Corrosion.

Question 38

Combined action of corrosion and metal loss due to rapidly moving fluids and/or solid particles.

Answer 38

Erosion Corrosion.

Question 39

Numerous small pits growing together or a few large pits that connect only after they have grown to a certain size.

Answer 39

Interconnected Pitting.

Question 40

Mechanisms which include SCC, corrosion fatigue, SSC, HIC, etc.

Answer 40

Environmental Cracking.

Question 41

Etching or near uniform attack with just a few scattered pits.

Answer 41

General Metal Loss with No Pitting.

Question 42

Special features such as cup-type hemispherical pits, pits within pits, striations parallel to the longitudinal axis of the pipe, tunnels in the end walls of pits, etc.

Answer 42

Unique Pit Morphology.

Question 43

Uniform attack of the pipe wall.

Answer 43

Etching or General Loss with no Pitting.

Question 44

Pits occur singularly or in groups but the pits are not interconnected.

Answer 44

Isolated Pitting.

Question 45

_Preferential attack of the weld metal or heat affected zone of the parent metal.

Answer 45

Selective Attack at Welds.

Question 46

Measurement of the deepest pit depth and the average pit depth.

Answer 46

Maximum / Average pit depth.

Question 47

Measurement of wall thickness every 0.25 inches along the longitudinal axis in the deepest areas of interconnected corrosion.

Answer 47

Profile of wall loss.

Question 48

Measurement of the deepest corrosion or thinnest wall caused by corrosion.

Answer 48

Maximum wall loss.

Question 49

Measurement of the greatest pit diameter and average pit diameter.

Answer 49

Maximum / Average pit diameter.

Question 50

Examining the typical length and width of pits to determine if there is a preferred orientation to the pitting.

Answer 50

Pit length vs pit width.

Question 51

A description of how far the corrosion extends down the longitudinal axis of the pipe.

Answer 51

Longitudinal extent.

Question 52

A description of how far the corrosion is present about the circumference of the pipe.

Answer 52

Circumferential extent.

Question 53

Calculation of both average depth / average diameter and maximum depth / maximum diameter ratios.

Answer 53

Depth / Diameter ratio.

Question 54

Name the five factors other than morphology or physical appearance that the author says should be considered by a competent corrosion investigator before making a conclusion.

Answer 54

1) Chemistry, 2) Electrochemistry, 3) Microbiology, 4) Metallurgy, and 5) Physical conditions such as temperature and flow velocity.

Question 55

Name the three main areas of managing internal corrosion of pipelines according to the author.

Answer 55

1) Detecting the corrosion, 2) Determining the cause of the corrosion, and 3) Mitigating (controlling) the corrosion.

Question 56

Which of the three main areas of managing internal corrosion of pipelines is the text book concerned with?

Answer 56

Determining the cause of the corrosion.

Question 57

Name the six “Who” questions that are essential in an investigative plan.

Answer 57

1) Who will do the investigative work?
2) Who will collect samples, both at the investigation site and at gas/liquid source locations?
3) Who is responsible for documenting the investigation and writing a report, if needed?
4) Who will decide if outside laboratory services are needed?
5) Who will stock and maintain testing supplies for future investigations?
6) Who needs to receive information about the investigation?

Question 58

Name the four “What questions that must be answered for an investigative plan.

Answer 58

1) What types of testing will be conducted, both immediately and later in the laboratory?
2) What samples must be collected?
3) What tools and supplies are needed to perform the testing and preserve any samples collected?
4) What are the relevant health and safety issues associated with a field investigation?

Question 59

Name the three “Where” questions essential to an investigative plan.

Answer 59

1) Where will the investigation be performed?
2) Where will field investigation supplies be stored for quick access?
3) Where do samples need to be sent for analysis?

Question 60

Name the three “When” questions for an investigative plan.`

Answer 60

1) When are the company “corrosion detectives” called in on the scene? And, will there be enough time to get the evidence needed?
2) When are certain types of tests performed?
3) When or how quickly does the cause of the corrosion need to be determined?

Question 61

List the two “How” questions that must be determined when developing an investigative plan.

Answer 61

1) How do we collect and analyze chemical and biological samples?
2) How does one interpret test data and reach a conclusion about the cause of the internal corrosion?

Question 62

What are the three general regulatory areas to consider when complying with state, federal, and other jurisdictional regulations?

Answer 62

1) Human health and safety
2) Environmental impact
3) Operational compliance

Question 63

Name the three main categories of evidence to consider when gaining a perspective on internal pipeline corrosion.

Answer 63

1) Visual evidence
2) Physical evidence
3) Circumstantial evidence

Question 64

Name the five measurement tools the author suggests to collect measurable visual evidence.

Answer 64

1) Steel tape measure.
2) Small finely divided steel ruler
3) Pit gauge
4) Pipe micrometer
5) Ultrasonic thickness gauge