Corrosion of Residential Aboveground Heating Oil Tanks: An Overview
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Corrosion of Residential Aboveground Heating Oil Tanks: An Overview Marina Banuta • Isabelle Tarquini
Submitted: 28 September 2009 / in revised form: 18 December 2009 / Published online: 7 January 2010 ASM International 2010
Abstract Three basic modes of failure are known for oil tanks: manufacturing defects, mechanical damage, and corrosion. Most of the tanks currently in use and manufactured in or prior to the 90s, are subject to leaking caused by internal corrosion. Corrosion-induced leakage always results in environmental damage by underground and/or aboveground oil contamination. Considering the costs related to decontamination and to replacement of residential tanks, the possibility of corrosion should be carefully addressed. To accomplish this task, the most common issues related to tank corrosion must be recognized and understood. This article is an overview of the corrosion mechanisms in aboveground residential tanks made of noncoated mild steel. Keywords Pitting corrosion Oil tanks Water Heating oil
Introduction Heating oil tanks are very popular components of residential heating systems in North-America. Their life service usually ranges between 10 and 15 years but can be significantly longer. However, in some cases premature shell perforation occurred after only one to two years of service [1]. The great majority of the residential tank leaks evaluated becomes the object of failure analysis because of the need to assess the responsibility for the spilling. Even though heating oil tank leakages are seldom a spectacular
M. Banuta (&) I. Tarquini SGS Canada, Materials Engineering, Montreal, QC, Canada e-mail: [email protected]
event, spilling from residential tanks may cause material and environmental damage and can affect lives and homes. This article will try to provide insight into the degradation phenomena and explain why tanks fail and what to do to minimize the unwanted leakage. Unfortunately, the failure analyst is (almost) always called late to failures that have potential litigations, thus, it is very difficult to achieve the goal of prevention. However, the authors sincerely hope that after reading this article, some one will take time to spread the message and advice relatives, friends, or neighbors who possess one of these tanks and begin the use of ‘‘backyard prevention technologies.’’ Figure 1 shows a sketch of an aboveground heating oil residential tank, manufactured according to Canadian standard CAN/ULC-S602: Aboveground Steel Tanks for Fuel Oil and Lubricating Oil. While the latest version of this standard was released in 2003, it must be noted that the great majority of the tanks still in use were made in accordance to the 1992 version, thus demonstrating that tank lifetimes generally exceed 10 years. The most common residential tank has a maximum nominal capacity of 1200 l, and a minimum shell thickness of about 2 mm (0.078 in.). The tank is made of welding quality mild steel, in accordance with the latest edition of ASTM A569 and/or CAN3-G40.21M 230G or a reco
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