Highly corrosion-resistant plated steel and manufacturing method therefor

Abstract

The present disclosure provides a highly corrosion-resistant plated steel having excellent corrosion resistance and a method of manufacturing the same. According to an embodiment of the present invention, the method of manufacturing the highly corrosion-resistant plated steel includes immersing a base steel in a hot-dip alloy-plating bath including 6% to 18% by weight of aluminum (Al), 3% to 6% by weight of magnesium (Mg), the remainder being zinc (Zn) and other inevitable impurities; taking the immersed base steel out of the hot-dip alloy-plating bath to form a hot-dip alloy-plated layer on the base steel; and cooling the base steel having the hot-dip alloy-plated layer thereon, wherein the content ratio of aluminum:magnesium in the hot-dip alloy-plating bath is 2:1 to 6:1.

1 . A method of manufacturing a highly corrosion-resistant plated steel, the method comprising:
 immersing a base steel in a hot-dip alloy-plating bath comprising 6% to 18% by weight of aluminum (Al), 3% to 6% by weight of magnesium (Mg), the remainder being zinc (Zn) and other inevitable impurities;   taking the immersed base steel out of the hot-dip alloy-plating bath to form a hot-dip alloy-plated layer on the base steel; and   cooling the base steel having the hot-dip alloy-plated layer thereon,   wherein a content ratio of aluminum:magnesium in the hot-dip alloy-plating bath is 2:1 to 6:1.   
     
     
         2 . The method according to  claim 1 , wherein the hot-dip alloy-plating bath is maintained in a temperature range of 420° C. to 500° C. 
     
     
         3 . The method according to  claim 1 , wherein the hot-dip alloy-plating bath is maintained at a temperature increased by 20° C. to 50° C. from a melting point of a molten hot-dip alloy. 
     
     
         4 . The method according to  claim 1 , wherein the cooling is performed at a cooling rate of 7° C./sec to 30° C./sec. 
     
     
         5 . The method according to  claim 1 , wherein the cooling is performed at a cooling rate of 10° C./sec to 15° C./sec. 
     
     
         6 . The method according to  claim 1 , wherein the hot-dip alloy-plated layer comprises a plated base layer and a Fe—Al alloy layer, and
 a total thickness of the hot-dip alloy-plated layer is twice or more a thickness of the Fe—Al alloy layer. 
 
     
     
         7 . The method according to  claim 6 , wherein the plated base layer comprises a primary Al phase, an Al/Zn eutectoid phase, or both. 
     
     
         8 . The method according to  claim 7 , wherein an area fraction of the primary Al phase, the Al/Zn eutectoid phase, or both in the hot-dip alloy-plated layer is in a range of 20% to 60%. 
     
     
         9 . A highly corrosion-resistant plated steel, comprising:
 a base steel; and   a plated layer formed on the base steel comprising 6% to 18% by weight of aluminum (Al), 3% to 6% by weight of magnesium (Mg), the remainder being zinc (Zn) and other inevitable impurities,   wherein the hot-dip alloy-plated layer comprises a plated base layer and a Fe—Al alloy layer,   the plated base layer comprises a primary Al phase, an Al/Zn eutectoid phase, or both, and   an area fraction of the primary Al phase, the Al/Zn eutectoid phase, or both in the hot-dip alloy-plated layer is in a range of 20% to 60%.   
     
     
         10 . The plated steel according to  claim 9 , wherein the plated layer comprises a plated base layer and a Fe—Al alloy layer, and a total thickness of the hot-dip alloy-plated layer is twice or more a thickness of the Fe—Al alloy layer. 
     
     
         11 . The plated steel according to  claim 9 , wherein a content ratio of aluminum:magnesium in the plated layer is in a range of 2:1 to 6:1. 
     
     
         12 . The plated steel according to  claim 9  wherein the plated layer is obtained from a hot-dip alloy-plating bath.