자동차용 에폭시계 양이온형 전착도료의 내식성에 대한 연구

이승엽; 이종무; 곽삼탁; 문명준; 서차수; Soung-Youb Lee; Jung-Mu Lee; Sam-Tag Kwag; Myung-Jun Moon; Cha-Soo Suh

Journal of the Korean Industrial and Engineering Chemistry, Vol.16, No.2, 250-256, April, 2005

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자동차용 에폭시계 양이온형 전착도료의 내식성에 대한 연구

Corrosion Behavior of Cathodic Electrodeposited Epoxy Based Coating for Automotive Primer

이승엽, 이종무¹, 곽삼탁¹, 문명준¹, 서차수 ^{1, †}

동주산업주식회사
¹부경대학교 공과대학 응용화학공학부

Soung-Youb Lee, Jung-Mu Lee¹, Sam-Tag Kwag¹, Myung-Jun Moon¹, and Cha-Soo Suh^{1, †}

Dongju Industrial Co., Busan 608-080, Korea
¹Department of Industrial Chemistry, Division of Applied Chemical Engineering, Pukyong National University, Busan 608-739, Korea

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초록

자동차 산업에서의 도장 외관은 아주 중요하다. 이러한 도장외관의 향상을 위해서 기본적으로 도막의 내식성과 밀착성이 해결되어야 한다. 도막의 물성의 향상을 위해서 금속의 화성피막은 매우 중요한 요소가 되고 있다. 전착도장 중 음극에서의 pH는 12 정도까지 증가하고, 이 같은 강알카리 조건에서 금속과 화성피막의 용해가 일어난다. 이 같은 현상의 화성피막과 소재사이의 결합력을 감소시키게 된다. 일반적으로 인산염 피막구조는 hopeite 및 phosphphylife 구조를 갖지만 hopeite 피막 구조보다는 phosphophyllite 피막구조가 내식성이 보다 우수하고, 양이온 전착도료에 의한 전착도장에서 강알카리화된 계면에서 피막의 알카리 용해성이 적어 내수밀착성의 향상을 보인다. Ni, Mn 등의 보조금속의 첨가는 P-ratio (phosphophyllite/ hopeite + phosphophyllite)를 증가시키므로 내수 밀착성과 내식성을 향상시키게 됨을 알 수 있었다.

Coating appearance is the most important problem in automotive industry. To increase the coating appearance quality, the corrosion resistance and the coating adhesion on metal substrates must be basically solved. The phosphating film made by the pretreatment of metal substrate is important factor to increase the coating adhesion. During the cathodic electrodeposition, the pH at the cathode surface increases up to about 12. In such a highly alkaline condition, the dissolution of metal substrate and phosphate film occurs. These phenomena result in the decrease of the bonding strength between the phosphating film and the substrate. Generally, the structure of zinc phosphating film is hopeite or phosphophyllite. It has been known that the phosphophyllite film contains better corrosion resistance and paint adhesion for hot water immersion test because of the decrease of dissolving amount of both metal substrate and phosphating film during the cathodic electrodeposition. It is found that the addition of Ni and Mn composition increase P-ratio and then can improve the paint adhesion on metal surface and the corrosion resistance.

Keywords:cathodic electrodeposition;phosphophyllite;zinc phosphating;corrosion behavior;automotive primer

[References]

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Takashi A, J. Iron Steel Inst. Jpn, 77, 861 (1991)
Schoff CK, Electrodeposion Training Manual, PPG Industries (1993)
Sumie N, Japan Finish., 10, 81 (1982)
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[Related Articles]

[1] Pierce PE, J. Coat. Technol., 53, 52 (1981)

[2] Maeda S, Asai T, Okada H, Corros. Engin., 31, 268 (1982)

[3] Takashi A, J. Iron Steel Inst. Jpn, 77, 861 (1991)

[4] Schoff CK, Electrodeposion Training Manual, PPG Industries (1993)

[5] Sumie N, Japan Finish., 10, 81 (1982)

[6] Lee GW, The Paint Finish, 22, 50 (1981)

[7] Watanabe T, Ishida Y, J. Met. Finish. Soc. Jpn., 29, 682 (1988)

[8] Kargol JA, Jordan DL, Corrosion, 38, 201 (1982)

[9] Lorin G, Phosphating of metal, Finishing publication Ltd. (1974)

[10] Machu W, Handbook of Electropainting Technology, Electrochemical publication ltd. (1978)

[11] Wismer M, Bosso JF, Chem. Eng., 14, 114 (1971)

[12] Freeman DB, Phosphating and metal pre-treatment, WoodheadFaulkner Ltd. (1986)

[13] Hurushi O, Japan Finish., 10, 149 (1982)

[14] GM Test Method, GM M9301.

[15] Pawlig O, Trettin R, Mater. Res. Bull., 34(12-13), 1959 (1999)

[16] Wyvill RD, Cape T, Prod. Finish., 52, 68 (1987)

[17] Sato N, Minami T, Kono H, J. Mat. Finish. Soc. Japan, 38, 571 (1987)

[18] Sato N, Minami T, Surf. Coat. Technol., 34, 331 (1988)

[19] Okada H, Miyawaki T, Miyaji M, Bosei Kanri, 26, 254 (1982)