Corrosion behavior of titanium in formic acid, oxalic acid, and formaldehyde

Tadafumi Kurogi, DDS,(a) Shigeru Nakamura, DDS,(a) Marie Koike, DDS, PhD,(a) Motohiro Terano, DDS,(a) Kunihiro Hisatsune, PhD,(b) and Hiroyuki Fujii, DDS, PhD(a)

(a)Division of Removable Prosthodontics and Management of Oral Function, and (b)Division of Dental and Biomedical Materials Science, Department of Development and Reconstructive Medicine, Course of Medical and Dental Sciences, Graduate School of Biomedical Sciences, Nagasaki University, Nagasaki, Japan

Purpose: The purpose of the present study is to evaluate the influence of formic acid, oxalic acid, and formaldehyde on corrosion behavior of cast titanium.
Materials and Methods: Cast titanium specimens were immersed in 128 mmol/L formic acid, oxalic acid, and formaldehyde, and in 64 mmol/L oxalic acid for three weeks. Color change, weight loss, surface chemical binding state, and solubility of titanium were determined after immersion in the four solutions, and the changes in properties of the titanium surface were examined after immersion in 128 mmol/L oxalic acid.
Results: The discoloration of titanium specimens was significantly greater in formic acid than in either oxalic acid or formaldehyde. Both the weight loss and amount of titanium ions dissolved from specimens in oxalic acid were greater than the corresponding values after immersion in formic acid and formaldehyde. The superficial titanium oxide layer in post-immersion specimens was thickest in formic acid, followed by oxalic acid and formaldehyde.
Conclusion: The oxalic acid corroded titanium. The results may have important clinical implications for conditions such as titanium allergy and incompatibleness. (Int Chin J Dent 2006; 6: 1-7.)

Key Words: corrosion, formaldehyde, formic acid, oxalic acid, titanium.