CORROSION PROTECTION WITH AL/ZN-BASED COATINGS

• Main Authors: LIU QIYANG, SMITH ROSS MCDOWALL, NOLAN DAVID JAMES, NEUFELD AARON KIFFER, RENSHAW WAYNE, WILLIAMS JOE, SHEDDEN BRYAN ANDREW
• Format: Patent
• Language: English; Korean
• Published: 15.06.2015
• Subjects: CHEMICAL SURFACE TREATMENT; CHEMISTRY; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING MATERIAL WITH METALLIC MATERIAL; COATING METALLIC MATERIAL; DIFFUSION TREATMENT OF METALLIC MATERIAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; METALLURGY; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION

Discoloring of Al/Zn-based steel strip into red and green colors when exposed to ′acid rain′ or under ′polluted environment′ can be minimized through the use of Al-Zn-Si-Mg alloy coating material of which the OT:SDAS ratio exceeds 0.5:1; wherein OT means overlay thickness on the surface of a strip and SDAS is a reference for arm intervals of a second dendrite for Al-sufficient alpha phase dendrite among the coating materials. Discoloring into red and green upon exposure to ′acid rain′ or under ′polluted environment′ and corrosion on an end edge of a cut in an offshore environment can be minimized in Al-Zn-Si-Mg alloy coating material on a steel strip by selecting compounds (mostly Mg and Si), solidifying control (mostly by cooling speed), and forming a particle of a certain shape on Mg_2Si on a channel between the dendrites. The present invention comprises: (a) a step wherein a metal strip is passed through a molten bath of Al-Zn-Si-Mg alloy, and coating is created on one side or both sides of the strip; and (b) a step wherein the coating is solidified on the strip to form a coating which has a micro structure including inter-dendritic channels of the compound on the Zn-sufficient process extended from a metal strip wherein anti-corrosion Al-Zn-Si-Mg alloy coating is formed on the metal, or in most cases steel strip to resist against ′acid rain′ or ′polluted environment′. An embodiment of the present invention includes a step wherein a coating is formed with an OT:SDAS ratio which exceeds 0.5:1 through the control of steps (a) and (b) wherein OT is an overlay thickness and SDAS is the arm interval of a second dendrite on Al-sufficient alpha of the coating material. "산성비" 또는 "오염된" 환경에서 Al/Zn-코팅된 강철 스트립의 적녹 변색은 OT:SDAS 비율이 0.5:1의 값을 초과하는 Al-Zn-Si-Mg 합금 코팅물로서 코팅물을 형성함으로써 최소화될 수 있으며, 여기서 OT는 스트립의 표면 상의 오버레이 두께이고, SDAS는 코팅물 중의 Al-풍부 알파상 덴드라이트에 대한 2차 덴드라이트 암 간격의 척도이다. "산성비" 또는 "오염된" 환경에서의 적녹 변색 및 해양 환경에서의 절단된 가장자리에서의 부식은 조성물의 선택(주로, Mg 및 Si), 및 응고 제어에 의해(주로, 냉각 속도에 의해), 그리고 덴드라이트 간 채널 중의 특정한 형태의 MgSi 상 입자를 형성함으로써 강철 스트립 상의 Al-Zn-Si-Mg 합금 코팅물에서 최소화될 수 있다.