73 Copyright 2020 | Philippine Engineering Journal Phil. Eng’g J. 2020; 41(2): 73-86 S.L. Santos and M.G. Mena Pitting Corrosion of Steinmann Stainless Steel Pins in Simulated Body Fluid Using Cyclic Polarization Technique Stephanie L. Santos and Manolo G. Mena Department of Mining, Metallurgical and Materials Engineering, College of Engineering University of the Philippines Diliman, Quezon City Abstract – Locally available Steinmann stainless steel pins were subjected to cyclic voltammetry in Kokubo simulated body fluid after immersion in SBF from 0 to 7 days. Results showed that the pins were susceptible to pitting corrosion from Day 0, with the degree of pitting increasing with the length of immersion. This may be due to the degradation of the initial passivation on the steel by SBF solution. SEM EDX analysis showed the presence of chloride precipitates in the pitting area. Chloride is known to induce autocatalytic corrosion of stainless steels. Optical Emission Spectroscopic analysis of the samples showed that one sample is SS304 and the other two were SS316L. The SS304 pins showed a higher tendency towards pitting corrosion when compared with the SS316L pins. Keywords – Steinmann pins, pitting corrosion, cyclic polarization I. INTRODUCTION Steinmann pins are one of the most common devices used in orthopaedic surgeries. It is a metallic rod with a trocar tip used for the initial fixation of fractured bones together. Steinmann pins are commonly made of surgical austenitic 316L stainless steel. Although well known for its biocompatibility, high mechanical strength and corrosion resistance, these materials still fail under severely corrosive environments such as human body fluid with high chloride concentration. As such, the suggested medical practice is to replace the 316L Steinmann pins with permanent implants such as Ti6Al4V alloys within two weeks. When the implant is placed inside the human body, it is continuously exposed to extracellular tissue fluid and surface undergoes electrochemical dissolution releasing nickel, chromium and iron ions, powerful allergens and carcinogens resulting into sepsis in the tissues surrounding the implant. Pins retrieved from patients showed that corrosion due to pitting is the most common observable failure. The contraction of sepsis and infection due to Steinmann pin corrosion is one of the problems in the orthopedic field in the Philippines. Commercially available pins are currently being sold without government inspection and quality control. The Philippine Orthopedic center alone inserted Steinmann pins into 1832 patients in 2015 [1]. The estimated usage worldwide is 1M orthopedic surgeries and expected to double by 2022 as the world’s population and life expectancy increases [2]. This study will characterize locally available PHILIPPINE ENGINEERING JOURNAL PEJ 2020; Vol. 41, No. 2: 73-86