Corrosion of Metals in Tropical Environments (Part 1—Five Non-Ferrous Metals and a Structural Steel)★

Abstract

An extensive investigation has been in progress since 1940 in the Panama Canal Zone to study the corrosion rates and characteristics of fifty different metals and alloys exposed to five natural tropical environments for periods of one, two, four, eight, and sixteen years. Up to the present, specimens through the eight year period have been removed and examined. The report describes the corrosion rate of aluminum, lead, nickel, zinc, and copper along with structural steel. Corrosion data for these metals as observed in the five environments have been obtained from weight loss and pitting measurements, visual inspection and physical property studies. Corrosion rates for these metals in the tropics are related to corrosion rates previously reported for these metals in temperate latitudes. 2.2.2

Bi-modal trends in the long-term corrosion of copper and high copper alloys

“…Another long-term test program [30] for the atmospheric corrosion of copper alloys took observations only at a small number of points in time, insufficient for use herein. The most extensive set of corrosion loss and pit depth data for copper and copper based alloys was found to be those obtained in the 16 year exposure experiments in the Panama Canal Zone (PCZ) conducted in the period just after the Second World War when it was realised that there was very little data for corrosion in tropical climates [19,31]. In this work observations were made at 1, 2, 4, 8 and 16 years of exposure from which mass loss, maximum pit depth and the average of the 20 deepest pits (from 4 faces of duplicate coupons) were derived.…”

“…3. The metric conversions of the corrosion loss data reported by Forgeson et al [31] and Hummer et al [19] are shown. As before best fit smooth curves obtained using a Stineman [33] function have been plotted through each data set.…”

“…In each case the trends are bi-modal, without any interpretation being required. Data from [19,31]. Fig.…”

“…Apart from pure copper, the trends are inconsistent with the power law and can be interpreted as showing a bi-modal characteristic. Data from [19,31]. Fig.…”

Engineered Barrier System: Physical and Chemical Environment

“…The freshwater rates are representative of those solutions that are dilute, such as lake water and J-13 well water. The saltwater rates are for ocean water with an average chloride content of 17,115-17,357 ppm (Forgeson et al 1958 [DIRS 159343]), and are used when the natural waters have been concentrated due to evaporation or contact with engineered materials. Any modifications to these definitions will be discussed for each individual material in the following sections.…”