Failure Analyses

EPA Finds Moderate or Severe Corrosion in Most Underground Diesel Tanks

In a new report on corrosion inside underground storage tanks storing diesel fuel, the U.S. Environmental Protection Agency found moderate or severe corrosion could affect metal components inside both steel and fiberglass tank systems.

Results Posted for NACE International’s 2016 Annual Corrosion Career Survey

Average annual salaries in 2016 are reported for corrosion professionals in the United States, Canada, United Kingdom, and Europe. A slight gain was seen for the United States and United Kingdom, while a larger increase was recorded in Canada.

Corrosion Inspection by 3D Non-Contact Profilometry

Corrosion can either take place locally to form a pit or crack, or it can extend uniformly across a wide surface. Proper surface analysis of the corroded sample is vital for evaluating corrosion characteristics and mechanisms, so the best materials, protective coatings, and corrosion-control measures can be selected.

NACE International’s Annual Corrosion Career Survey Results for 2015

Corrosion professionals in North America and Europe have experienced another year of continued growth in career opportunities and salary levels, according to the 2015 Corrosion Career Survey conducted by Materials Performance magazine.

Wanted: Technical Articles for MP

To successfully communicate the wide variety of corrosion-related issues affecting corrosion professionals today, MP is actively encouraging corrosion control professionals worldwide to submit technical articles to share their corrosion-related experiences with over 36,000 NACE International members around the globe.

SCC Failure of a Super Duplex Separator Vessel in an Ammonium Nitrate Plant

This article presents findings of a failure investigation on a separator vessel in an ammonium nitrate (NH4NO3) plant. The super duplex stainless steel vessel leaked due to stress corrosion cracking initiated in the heat-affected zones of welds exposed to the NH4NO3 solution at ~180 °C.

Failure Analysis of Pyrolysis Furnace Transfer Line Tubes

Transfer line tubes of an ethane pyrolysis furnace, operating at 850 ±20 °C and 1.0 atm pressure, developed longitudinal cracks after less than one third of their expected service life. The tubes were constructed of Fe-based UNS N08810 alloy with a wall thickness of 10 mm. Metallurgical evaluation revealed that the mode of failure was high-temperature carburization attack leading to intergranular cracking. The cause of failure was overheating, likely to have occurred during decoking operations. Better control of furnace temperature was recommended to avoid overheating. Alternatively, a wrought alloy capable of developing highly protective aluminum oxide (Al2O3)-base scale such as Ni-based UNS N07214 could be used as a replacement.

Microbiologically Influenced Corrosion in a Copper Tube Chiller

The increased use of recycled water has led to the need for an effective water treatment program to prevent microbiologically influenced corrosion (MIC). This article describes an investigation of copper tubes in a chiller that failed from MIC because of a poor water treatment program.

Premium Connection Downhole Tubing Corrosion

This article discusses a field background search, macro- and micro-corrosion morphology analysis, and material testing of corroded premium connection downhole tubing. Tubing failure was caused by erosion-corrosion from highly disturbed liquid and high shear stress at the couplings.

Unusual Occurrence Causes Leak in High-Pressure Underground Gas Pipeline

A gas leak was detected on a 56-in (1.4-m) crosscountry gas pipeline from a small orifice on the bottom of an indentation. The pipeline had an epoxy primer and a hot polyethylene coating, and was only four years old. Metallurgical tests on the hole and theoretical calculations indicated that the pipeline had been penetrated by a bullet before being coated. This may be the first such case recorded, and would have been difficult to prove if an explosion had taken place.

Stress Corrosion Cracking of a Vinyl Chloride Stripper Vessel

This article describes the findings of a detailed failure investigation on a UNS S32750 super duplex stainless steel vinyl chloride stripper vessel that experienced cracking at nearly half of the welds. The cracking was identified as Type A “active-passive” stress corrosion cracking, which initiated on the inside of the vessel at both the circumferential and longitudinal welds.

MIC Failure of Type 316L Seawater Pipeline

A Type 316L stainless steel (SS) (UNS S31600) pipeline carrying seawater suffered pitting and leakage within a few years of installation. Visual examination revealed penetrations and shallow pits. Electron probe microanalysis results indicated a decrease in chromium concentration within the pit and in the iron concentration at the pit periphery. Microbial investigation confirmed the presence of sulfate-reducing bacteria and chromium-, manganese-, and iron-oxidizing bacteria.

Failure Analysis, Part II—Case Histories

The academic side of failure analysis was presented in Part I of this article. This included 1) steps in conducting a failure analysis, 2) typical tools, and 3) theory of crack propagation. This article provides several case studies demonstrating the use of these techniques.

Stress Cracking of Stainless Steel Safety Gate Valve Stem

This study investigated the failure of a 15-5 PH (UNS S15500) precipitation-hardened stainless steel stem when installed in a 5 1/8-in (130-mm) hydraulic surface safety gate valve working in a sour gas environment. The results indicate that the fracture failure was caused by sulfide stress cracking, which progressed transgranularly in the martensitic matrix.

Failure of Glass-Reinforced Epoxy Material Piping Components on an Offshore Platform

Glass-reinforced epoxy (GRE) is a synergistic combination of two or more materials with a reinforcement of E-glass fiber. The brittle nature of the material demands careful handling during transportation, fabrication, and installation. This article describes the analysis of components that failed in a GRE piping system. The failed components were examined through destructive and nondestructive tests. The failure modes and analysis revealed that the combined effect of manufacturing defects and installation practices caused various types of failures.