• Clean Technology
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• v.9 no.2
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• pp.57-61
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• 2003

A novel nitric acid-free desmut solution has been developed to remove smut, which is produced from a NaOH etching, on the surface of aluminum alloy metal in metal surface treatment processes. Comparing with the performance of 5% $HNO_3$ desmut solution, the mixed acid solution containing 2% $H_2O_2$, 0.5% HF, and 10% $H_2SO_4$ shows the same effect of smut removal for aluminum alloy samples of A16061 and A15052. To examine the surface alterations of the aluminum samples, in addition, the surface analysis is carried out with scanning electron microscopy (SEM) and electron probe microanalysis (EPMA).

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.2
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• pp.109-115
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• 2022

The demand for metal 3D printing technology is increasing in various industries. The materials commonly used for metal 3D printing include aluminum alloys, titanium alloys, and stainless steel. In particular, for applications in the aviation and defense industry, aluminum alloy 3D printing parts are being produced. To improve the corrosion resistance in the 3D printed aluminum alloy outputs, a post-treatment process, such as chromate coating, should be applied. However, powdered materials, such as AlSi7Mg and AlSi10Mg, used for 3D printing, have a high silicon content; therefore, a suitable pretreatment is required for chromate coating. In the desmut step of the pretreatment process, the chromate coating can be formed only when a smut composed of silicon compounds or oxides is effectively removed. In this study, suitable desmut solutions for 3D printed AlSi7Mg and AlSi10Mg materials with high silicon contents were presented, and the chromate coating properties were studied accordingly. The smut removal effect was confirmed using an aqueous desmut solution composed of sulfuric, nitric, and hydrofluoric acids. Thus, a chromate coating was successfully formed. The surfaces of the aluminum alloys after desmut and chromate coating were analyzed using SEM and EDS.

• Journal of the Korean Society for Heat Treatment
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• v.31 no.1
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• pp.6-11
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• 2018

The anodic oxidation behavior of Si-containing aluminum alloy for diecasting was investigated. Especially, the property changes during anodization both on aluminum 1050 and 9 weight percentage silicon containing aluminum (Al-9Si) alloys were analyzed by the static current test. In order to fabricate a uniform anodic oxidation film by effect of Al-Si compound, nitric acid containing hydrofluoric acid had been used as a desmutter for aluminum alloy after alkaline etching. It was found that the level of voltage of Al-9Si alloy during the static current test was almost as double as higher than aluminum 1050 through anodization. By adding hydrofluoric acid in the nitric acid electrolyte, the silicon compound on the surface was removed, and the optimum amount of added hydrofluoric acid could be derived. It was also observed that the size of silicon compound formed on the surface could be refined by heat treatment at $500^{\circ}C$ and followed water quenching.