Metallic stripping on bronze pieces.
Metallic stripping on bronze pieces.
Problem
Appearance of defects in bronze products after pickling of different metallic layers (palladium, copper and nickel).
Objective
- Study the reaction mechanism between metals and pickling agents.
- Characterize the surface of the samples using electron microscopy (SEM).
- Characterization of the cross section of the samples by means of FIBSEM.
- Determine the problem and propose a solution.
ATRIA solution
To start the project, all the chemical reactions that could occur between the stripping agents for palladium, copper and nickel on bronze (the product’s base material) were studied. During this study, several incompatibilities were determined, so characterization tests of the samples were proposed after carrying out each of the process stages (palladium, copper and nickel). In this way, the aim was to detect the exact moment from which the damage to the bronze occurred in the stirring process. This characterization was carried out using scanning electron microscopy (SEM), which allows studying the morphology of the surface and analyzing its composition, thanks to the equipment’s X-ray detector (EDX).
In addition, to complete the characterization, the cross section of the metal samples was studied after each of the pickling stages (shoveling, copper and nickel). For this, a FIBSEM equipment was used, which allows to carry out the cut and observe the cross section by means of SEM + EDX. After characterizing all the samples, all the results obtained were studied and compared until the reason for the failure was determined. In this case, the problem was in the stripping of the nickel, which was incompatible with the tin contained in the bronze. Finally, alternatives were proposed to carry out nickel pickling with other less aggressive chemical agents.
