• 마이크로전자및패키징학회지
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• 제23권4호
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• pp.79-85
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• 2016

It is imperative to find environment-friendly coatings as an alternative to the currently used hexavalent chromate conversion coatings for the purpose of improving the anti-corrosion properties of aluminum alloys. Hence, in this study, the corrosion properties of a trivalent chromate conversion coating solution are analyzed and measured. Because of the presence of multiple components in trivalent chromate conversion coating solutions, it is difficult to control plating, attributed to their mutual organic relationship. It is of significance to determine the concentrations of the components present in these coatings; hence, qualitative and quantitative analysis is required. The coating solution contained not only an environment-friendly component chromium(III), but also zirconium, fluorine, sulfur, and potassium, in the coating film. These metals are confirmed to produce a film with improved corrosion resistance to form a thin layer. The excellent corrosion resistance for the trivalent chromate solution is attributed to various inorganic and organic additives.

• 공업화학
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• 제18권3호
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• pp.296-302
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• 2007

6가 크롬의 크로메이트 코팅제의 대체를 위한 3가 크롬의 크로메이트 코팅용액의 제조에 관한 것이다. 본 연구에서 제안된 코팅제는 3가 크롬원으로서 $KCr(SO_4)_2$를 35~45 g/L, 인산계 화합물로서 $NaH_2PO_4$를 20~30 g/L을 주성분으로 하고 여기에 금속계 황산화물로서 $CoSO_4$ 10~20 g/L, $ZnSO_4$ 10~20 g/L의 조성으로 구성된 것이다. 이 제안된 3가 크롬 코팅용액을 사용하여 pH 2.0~2.2, 상온에서 담지시간 20~25 s의 조건하에 시안아연도금체에 코팅된 피막은 염수분무시험결과 5% 백청발생까지 120 h 이상 견디는 우수한 내식성을 발현하였다.

• 한국표면공학회지
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• 제31권6호
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• pp.307-316
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• 1998

The effects of surface roughness on chromate conversion coating and the corrosion behavior of galvanized steel sheets were investigated. Surface roughness was differently given to the galvanized steel sheets tested and these were then chromated. Accelerated corrosion test was conducted under the condition of $30^{\circ}C$, 90%RH with flowing 200ppm $SO_2$ gas. The galvanized steels were also exposed to urban environment for 5 weeks. The corrosion rates were measured by weight gain method. The distribution of chromate film and corrosion product on the coating were examined which SEM/EDS. The chromate film formed preferentially at the convex sites rather than at the concave sites on the surface. The corrosion products were found at the concave sites where the chromate film formed rarely. The corrosion product on the coating were found at the concave sites where the chromate film formed rarely. The corrosion rates increased slightly with the surface roughness in accelerated corrosion test but significantly in field test.

• 한국기계가공학회지
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• 제21권2호
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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.

• 한국표면공학회지
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• 제37권4호
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• pp.200-207
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• 2004

Molybdate chemical conversion coating layer formed on EGI has been studied in view of corrosion resistance, surface morphologies, and phases formed. It was found that coating layer consists of$ MoO_3$, $MoO_2$, Mo oxides having lower valences than 4 and ZnO. It is interesting to note that the coating layer formed at high Mo concentration (30 g/l) in the temperature range of $40-60^{\circ}C$ exhibited relatively high corrosion resistance, although thickness of coating layer is nearly identical with those formed under the other conditions. It was believed that an increase of driving force due to high Mo concentration plays an important role in the formation of corrosion-resistant coating layer, probably due to tile formation of dense coating layer.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2006년도 전기학술대회논문집
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• pp.271-272
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• 2006

Zinc confers high corrosion resistance by acting as a sacrificial anode, and a zinc coating improves the appearance of steel. Chromate conversion coating (CCC) films are still one of the most efficient surface treatments for steel. Although such films can self-repair via the dissolution of Cr(VI), dissolved Cr(VI) have adverse effects on humans, and the environment. Therefore, we examined the corrosion protection property and morphology of colloidal silica conversion films as an alternative to CCC films. The corrosion behavior was investigated in 3% NaCl solution using electrochemical techniques, including electrochemical impedance spectroscopy, open circuit potential, and the salt spray test(SST). Corrosion was implied by the appearance of red rust on the specimen surface. In corrosion resistance at 3% NaCl solution, red rust appeared at 15-20, 55-70, and 83-98 days on Zn-electroplated steel, colloidal silica conversion-coated specimens, and CCC-coated specimens, respectively. In the salt spray test, the colloidal silica film provided better corrosion protection than CCC films, i.e., red rust appeared at 96 hours on the Zn-electroplated steel sheet, at 432 hours with the CCC films, and at 888 hours with silica conversion coating.

• 공업화학
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• 제17권5호
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• pp.433-442
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• 2006

금속표면처리 기술 분야에서 광범위하게 적용되어온 6가 크롬에 의한 부식억제방법은 더 이상 사용할 수 없는 단계에 이르렀다. 전 세계적으로 자동차 산업에 적용되기 시작한 이 6가 크롬사용에 대한 규제는 전자산업을 비롯한 모든 산업에 예외 없이 적용될 것이다. 이에 따라 새로운 부식억제 방법이 절대적으로 필요하며, 3가 크롬을 바탕으로 하는 새로운 부식억제 방법이 그 자리를 대신할 것이다. 따라서 본 총설에서는 6가 크로메이트 대체를 위한 화성코팅에 대한 공정 개발을 위해 현재까지 진행된 과정 및 제안된 3가 크롬화성코팅을 소개하여 획기적인 3가 크로메이트 화성코팅 공정의 확립에 기여하고자 한다.

• 한국해양공학회지
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• 제24권5호
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• pp.67-74
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• 2010

Chromate conversion coating is a coating technique used to passivate aluminum, zinc, cadmium, copper, silver, magnesium, tin, and their alloys to slow corrosion. The process uses various toxic chromium compounds, which may include hexavalent chromium. The industry is developing less toxic alternatives in order to comply with substance restriction legislation, such as RoHS. One alternative is to develop a Cr-free coating solution. In this study, eco-friendly, Cr-free solutions (urethane solution S-700, organic/inorganic solution with Si LRO-317) were used. Test specimens were dried in a drying oven at $190^{\circ}C$ for 3, 5, 7, and 9 minutes. Corrosion resistance was evaluated using a salt spray test for 72 hours. The results show that the optimum corrosion resistance was achieved at $190^{\circ}C$ for five minutes for EGI and three or five minutes for HDGI, respectively. The adhesive properties of the two types of coating solutions were superior regardless of drying time.