Graphitic corrosion in a XVIII century artillery piece

Abstract:

Laboratory tests were carried out on a piece of 18th-century artillery in advance state of deterioration due to the action of a marine environment. The piece presented a low-pH and chloride-contaminated yellowish liquid coming from the corroded area. The piece presented graphitic type corrosion with different characteristics than those observed in other case histories reported in the literature. The corrosion products presented as main compound the FeOOH -akaganeite and a network of graphite flakes. Metallographic observation of corrosion front revealed an irregular interface due to selective corrosion of ferrite in relation of cementite both from the pearlite and from ledeburite. Some procedures used in the restoration of archaeological iron pieces are discussed. For this case history, the use of hydrogen reduction process is recommended. If this process was not possible, electrolysis with low current densities was recomended.


Reference:
TSCHIPTSCHIN, A.; GONÇALVES, C.R.L.; GOLDENSTEIN, H.; WOLYNEC, S. Corrosão grafítica em peça de artilharia do século XVIII. In: CONGRESSO ANNUAL DA ABM,35., 6-11 jul.1980. São Paulo. Anais… São Paulo: ABM, 1980. p. 361-75.v.1. Também publicado em: Metalurgia – ABM, São Paulo, 37 (288): 629-34, nov.1981

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