Ref.: MmeCa09-027
Apresentador: Frederico Garcia Bindi Lacerda
Autores (Instituição): Simões, D.d.(Universidade do Estado do Rio de Janeiro); Lacerda, F.G.(Universidade do Estado do Rio de Janeiro); Diniz, M.G.(Universidade do Estado do Rio de Janeiro); Freitas, R.P.(Instituto Federal do Rio de Janeiro); Ferreira, D.S.(Instituto Federal do Rio de Janeiro); Pimenta, A.R.(Instituto Federal do Rio de Janeiro);
Resumo:
Automotive vehicles are highly valuable assets. Because of this, they are often the subject of robbery and theft. To allow for their traceability and location, each one has a unique serial number engraved on its chassis. In the "car cloning crime", this serial number is ground, and a new serial number is engraved where the previous one was. To identify the original serial number, the scientific police use special chemical reagents. In a procedure similar to metallographic chemical etching, a reagent is applied to the chassis surface. These reagents can identify the ground serial number as they react more strongly with the hardened region of the steel, which was below the erased marks of numbers. FRY reagent is the most commonly applied for that procedure, but the results are often unsatisfactory and need improvement. In this work, two modifications to the FRY reagent were tested to improve its performance: the replacement of copper chloride with iron chloride and anhydrous barium chloride. To enhance police officer safety during forensic activity, this work proposed the creation of a paste chemical FRY reagent. The paste chemical FRY reagent will reduce the risk of accidents with the transport and the use of chemical reagents in situations where the forensic procedure has to be carried out in the field. SAE 1020 steel sheets 2mm thick were engraved with the number 3 using a punch and a universal hydraulic testing machine. The load of 19.613 N ( 2 tons) was used to make the marks. To simulate adulteration, the sample was sanded with an emery machine until the marking was completely removed. The development test was carried out with three reagents: FRY (copper chloride, hydrochloric acid, and distilled water); FRY mod1 (iron chloride, hydrochloric acid, and distilled water); FRY mod2 (Anhydrous barium chloride, hydrochloric acid, and distilled water). The reagents were applied to the region using embedded cotton. The fry reagent made the number 3 visible again after 3 minutes of application. However, the tested variations, mod1 and mod2, failed to reveal the erased marking even after 20 minutes of application. The FRY paste was made using the FRY reagent and particles of alumina. It was possible to create a paste that efficiently revealed the erased marking when applied to the steel sheet. It was possible to identify that copper chloride played a fundamental role in identifying the hardening zone. The use of chemical paste reagents for field forensic activities shows promise, maintaining the reagent's efficiency and reducing the activity's dangerousness.