CFS Failure Analysis & Prevention 3

Question 1

Which environmental condition most accelerates galvanic corrosion between steel fasteners and aluminum structural members?

Accepted Answer

Presence of an electrolyte such as saltwater

Answer

Galvanic corrosion requires an electrolyte to conduct ionic current; saltwater dramatically increases conductivity and accelerates the corrosion cell between dissimilar metals.

Question 2

What is the primary purpose of performing a torque audit on in-service fasteners?

Accepted Answer

To detect loss of preload and potential loosening

Answer

A torque audit checks whether fasteners still have adequate clamp load by measuring the torque required to continue turning them, revealing any relaxation or loosening.

Question 3

Fretting wear on fastener contact surfaces is characterized by:

Accepted Answer

Red-brown iron oxide debris and surface pitting

Answer

Fretting produces fine metallic debris that oxidizes to form characteristic red-brown iron oxide powder, along with surface pitting at the contact interface.

Question 4

A fastener assembly in a chemical plant fails due to dealloying. Which alloy is most susceptible to dezincification?

Accepted Answer

Yellow brass (Cu-Zn)

Answer

Brass (copper-zinc alloys) is highly susceptible to dezincification, where zinc is selectively leached, leaving a weak, porous copper structure.

Question 5

During failure analysis, scanning electron microscopy (SEM) is primarily used to:

Accepted Answer

Examine fracture surface morphology at high magnification

Answer

SEM provides high-magnification, high-depth-of-field images of fracture surfaces, enabling identification of fatigue striations, intergranular patterns, and other failure signatures.

(CFS) Certified Fastener Specialist Practice Test

(CFS) Certified Fastener Specialist Practice Test

CFS Failure Analysis & Prevention 3