Interesting Failures

 

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Burleigh Corrosion Consultants LLC provides expert failure analysis for both metallic and corrosion failures. The following photographs show some interesting failures from Dr. Burleigh's files.


The SEM image shows microbes inside a pit in a copper pipe that was used for Santa Fe municipal water. The microbes were fixed in HMDS for preservation.

The SEM image shows a fracture face in an aluminum part that failed due to corrosion fatigue, which was initiated by pitting. The individual fatigue striations also show pitting, indicating that the pitting corrosion continued during service. Microbial induced corrosion is suspected in this case since sulfides were detected in the pits, but no chlorides.

The SEM image of a polished crossed-section of a copper tube exhibits ant-nest corrosion (also known as formicary corrosion). This type of copper corrosion is attributed to excess extrusion lubricants left on the copper surface, which can decompose during storage and form organic acids. The organic acids corrode the copper and leave cuprite (Cu2O) in the pits. This copper tubing exhibited pinhole leaks after being put into service.

The fracture surface of a bicycle ball bearing is shown by SEM. This ball bearing was removed from service because of a grinding noise. The bearing surface originally spalled most likely due to contact-stress fatigue with a subcase origin. (Photo by Dr. Burleigh for a report by Dominic Vasquez.)

This SEM image shows a polished and etched cross-section of a nickel-plated copper medalion. Although the top nickel-plate is uniform and good quality, the poor quality of the underlying surfaces caused problems during service. The middle copper-strike is non-uniform, and the base metal copper is over-etched, which led to porosity and poor bonding.

The SEM image is taken from a cellulose-acetate replica made from a fractured steel shaft. The fracture face resembles tension overload of a hydrogen embrittled, tempered, martensitic steel.

This heat sink used recycled cooling water to remove the excess heat from the attached electronics. A machined cut-away reveals severe erosion-corrosion at the elbows of aluminum heat sink. The erosion-corrosion occured when the pH of the cooling water exceeded 9.

The SEM image is a polished cross-section of the wall of a brass fitting which experienced dezincification in municipal water after eight years of service. The brass was a two-phase alloy (59Cu-39Zn-1Pb-1Sn) which could not withstand the high chloride, low carbonate water. The water side with the severe dezincification is on the left, and the unaffected brass is on the right. The bright spots are the high "Z" Pb-Sn phases. The black spots are holes in the metal due to the dissolution of the zinc.

A higher magnification SEM image is shown of the brass fitting in the above figure. Surface diffusion allows the Cu atoms to rearrange as the Zn atoms dissolve, which leaves a sponge-like metal that eventually allows water leaks.

Burleigh Corrosion Consultants invites you to describe your corrosion problem and we will provide you up to ten minutes of free consultation. For complex corrosion problems, please contact BCC, describe the problem and we will provide an estimate of the cost to solve the problem.

Contact BCC by e-mail, tdburleigh(at)corrosionhelp.com.

Mailing Address:

Burleigh Corrosion Consultants, LLC
301 School of Mines Rd
Socorro, NM 87801 USA
1-575-517-0672