ORIGINAL RESEARCH ARTICLE Copper Corrosion-Simulated Uterine Solutions J.M. Bastidas,* E. Cano,* and N. Mora* We studied the copper corrosion and product layers origi- nating in a simulated uterine solution at pH values 6.3 and 8.0 for 15, 65, 180, and 360 days at 37°C. Absorbance measurements were performed. Corrosion product layers on the copper surface were characterized by scanning electron microscopy, energy dispersive x-ray, and x-ray photo-electron spectroscopy techniques. Copper release for pH 6.3 and 8.0 was 3.4 – 4.5 g/day for 15 days and 0.1– 0.3 g/day for 360 days. Of the order of 30%– 40% of dissolved cupric ions were trapped in the product layers. The main compounds identified were cuprite (Cu 2 O), calcite (CaCO 3 ), and phosphates. CONTRACEPTION 2000;61: 395–399 © 2000 Elsevier Science Inc. All rights reserved. KEY WORDS: simulated uterine solution, intrauterine de- vice, copper corrosion, absorbance Introduction Z ipper et al. 1 demonstrated that the antifertility effect of an intrauterine device (IUD) can be improved by covering part of its surface. Though the mechanism of the contraceptive action of a copper-containing intrauterine device (Cu-IUD) is unclear, two hypotheses have been established. The first suggests that the dissolution of copper in uterine secretions and the formation of cupric ions leads to the inactivation of sperm and the suppression of myometrial contractions, 2,3 while the second pro- poses a sterile inflammation which is enhanced by copper. 4 Corrosion damage can limit the lifetime of a Cu- IUD. Though copper corrosion behavior and copper ion release have been extensively studied, the copper corrosion rate in an intrauterine environment has not been investigated to the same extent. Circumstances that obstruct copper release may have a negative influence on Cu-IUD effectiveness. The corrosion products and deposits formed at different times have scarcely been studied in the literature. It is generally accepted that pH is an important parameter for copper corrosion in an aqueous me- dium. Hydrogen ions can promote copper corrosion (2Cu + 4H + + O 2 3 2Cu 2+ + 2H 2 O). The pH value in uterine chemistry varies from one individual to an- other. Reported pH values from human uterine fluids range from 6.0 to 7.9. 5–7 However, this parameter has also been poorly studied in the literature. The aim of our research was to study the copper corrosion rate, using absorbance measurements, and to characterize the corrosion product layers and de- posits formed on copper specimens during periods of up to 360 days immersion in a simulated uterine solution at two pH values. Materials and Methods Copper specimens with a chemical composition (% mass): 0.009 Sn, 0.001 As, 0.001 Bi, 0.003 Ni, 0.001 Fe, 0.015 Pb, 0.001 Mn, 0.019 P, 0.0005 Ag, 0.001 S, 0.005 C, 0.002 Sb, 0.001 Al, and balance Cu were utilized. The specimens of dimen- sions 5.0 cm  5.0 cm were mechanically cut from sheets 1.0 mm thick and their surfaces were hand- polished with different grades of emery paper down to grade 600, degreased with acetone, rubbed energeti- cally with cotton wool soaked in ethanol, and finally dried at room temperature. Table 1 indicates the composition of the simulated uterine solution. 7 The pH values 6.3 and 8.0 were established by adding diluted hydrochloric acid or sodium hydroxide solution and the pH value was periodically adjusted throughout the exposure time. Experiments were performed at 37.0  0.1°C temper- ature and in triplicate, showing a reproducibility of more than 95%. The loss of metallic copper was determined by measuring the cupric ion content in the simulated uterine solution after 15, 65, 180, and 360 days. Diethyl ammonium salt of diethyldithiocarbamic acid was used. This compound forms a yellow chelate with the cupric ion, 2 with an absorption maximum at 446 nm. Absorbance (A) of the solutions using various *National Center for Metallurgical Research (CSIC), Avda. Gregorio del Amo 8, 28040 Madrid, Spain Name and address for correspondence: J.M. Bastidas, National Center for Metallurgical Research (CSIC), Avda. Gregorio del Amo 8, 28040 Madrid, Spain. Tel.: +34-91-553-89-00; Fax: +34-91-534-7425; E-mail: bastidas@ cenim.csic.es Submitted for publication February 23, 2000 Revised April 6, 2000 Accepted for publication April 6, 2000 © 2000 Elsevier Science Inc. All rights reserved. ISSN 0010-7824/00/$–see front matter 655 Avenue of the Americas, New York, NY 10010 PII S0010-7824(00)00124-4