Case Study: Analysis of Corrosion Patterns to Evaluate the Preaccident Configuration of an ATV Tie Rod End Connection

Abstract

A forensic investigation was performed on an ATV that was involved in an accident in which the vehicle struck a tree. Postaccident, the front knuckle/tie rod end connection was found to be loose. The prevailing torque nut was found positioned at the end of the tie rod end bolt such that there was a gap between the face of the nut and the knuckle. The subject nut exhibits machining asperities that resulted from close contact with the knuckle face. EDS analysis of the corrosion product ring on the knuckle face revealed the corrosion product was zinc oxide, which had formed due to galvanic corrosion between the galvanized nut and the carbon steel knuckle. Scuffing patterns on the nut, wear patterns on the bolt, and lack of damage to the knuckle corrosion ring confirmed that the nut could not have loosened from the as-manufactured position to the postaccident position. No viable nut loosening mechanism was identified other than deliberate, manual manipulation.