达克罗膜层性能测试

随着人们对环境的高度关注以及紧固件产品性能的要求越来越高，对汽车紧固件国外已明确建议≧10.9级高强度螺栓使用达克罗涂层防腐，电镀时不允许电解或电解离析的镀层。 　　近年，为了提高紧固件镀层的耐蚀性能，达克罗技术已正式列入国家标准，GB/T18684-2002《锌铬涂层技术条件》和汽车行业标准QC/T721-2004《汽车用锌铝铬涂层》。达克罗膜具有优异的防腐蚀性能，是由其特殊的结构所决定的。故膜层性能的测试就显得十分重要。 　　一、 达克罗涂层的外观 　　达克罗涂层呈银灰色，经改性可以获得其它颜色（如黑色等），涂层颜色均匀一致，不允许漏涂，有气泡、遮盖力弱、流挂、划伤、堆积、变色及其它缺陷。 　　二、 达克罗涂层的附着量和等级 DING-RIGHT: 5.4pt; BORDER-TOP: windowtext 1pt solid; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext 1pt solid; WIDTH: 106.5pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt" width="142"> 防护等级 DING-RIGHT: 5.4pt; BORDER-TOP: windowtext 1pt solid; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #c1ccd9; WIDTH: 106.5pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" width="142"> 附着量 g/m2 DING-RIGHT: 5.4pt; BORDER-TOP: windowtext 1pt solid; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #c1ccd9; WIDTH: 106.55pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" width="142"> 涂层厚度 μm DING-RIGHT: 5.4pt; BORDER-TOP: windowtext 1pt solid; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #c1ccd9; WIDTH: 106.55pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt" width="142"> 工艺 DING-RIGHT: 5.4pt; BORDER-TOP: #c1ccd9; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext 1pt solid; WIDTH: 106.5pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; HEIGHT: 27.95pt; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="142"> 1 DING-RIGHT: 5.4pt; BORDER-TOP: #c1ccd9; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #c1ccd9; WIDTH: 106.5pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; HEIGHT: 27.95pt; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="142"> ≧16 DING-RIGHT: 5.4pt; BORDER-TOP: #c1ccd9; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #c1ccd9; WIDTH: 106.55pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; HEIGHT: 27.95pt; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="142"> 4-6 DING-RIGHT: 5.4pt; BORDER-TOP: #c1ccd9; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #c1ccd9; WIDTH: 106.55pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; HEIGHT: 27.95pt; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="142"> 一涂一烘 DING-RIGHT: 5.4pt; BORDER-TOP: #c1ccd9; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext 1pt solid; WIDTH: 106.5pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; HEIGHT: 31pt; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="142"> 2 DING-RIGHT: 5.4pt; BORDER-TOP: #c1ccd9; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #c1ccd9; WIDTH: 106.5pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; HEIGHT: 31pt; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="142"> ≧22 DING-RIGHT: 5.4pt; BORDER-TOP: #c1ccd9; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #c1ccd9; WIDTH: 106.55pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; HEIGHT: 31pt; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="142"> 6-8 DING-RIGHT: 5.4pt; BORDER-TOP: #c1ccd9; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #c1ccd9; WIDTH: 106.55pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; HEIGHT: 31pt; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="142"> 二涂二烘 DING-RIGHT: 5.4pt; BORDER-TOP: #c1ccd9; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext 1pt solid; WIDTH: 106.5pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; HEIGHT: 34.1pt; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="142"> 3 DING-RIGHT: 5.4pt; BORDER-TOP: #c1ccd9; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #c1ccd9; WIDTH: 106.5pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; HEIGHT: 34.1pt; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="142"> ≧34 DING-RIGHT: 5.4pt; BORDER-TOP: #c1ccd9; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #c1ccd9; WIDTH: 106.55pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; HEIGHT: 34.1pt; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="142"> 8-10 DING-RIGHT: 5.4pt; BORDER-TOP: #c1ccd9; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: #c1ccd9; WIDTH: 106.55pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; HEIGHT: 34.1pt; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt" width="142"> 三涂三烘 　　不同的紧固件在不同的工作环境，可根据实际情况采取的不同工艺，在一般腐蚀环境下使用，防护等级≦2级，多采用二涂二烘；在严酷腐蚀环境下使用防护等级3级，则采用三涂三烘。 　　涂层的厚度检验一般可采用金相显微镜法和磁性测厚仪进行。附着量试验采用溶解称重法，即将涂覆有达克罗膜的零件浸渍在温度为70℃～80℃的20%NaOH的水溶液中10min，让涂层全部溶解。称量溶解前后质量的变化，精确至0.001g，根据面积的大小即可计算附着量。 　　三、 达克罗涂层的耐蚀性 　　耐腐蚀性可按中性盐雾试验GB/T10125的规定，防护等级1、2、3级，出现红锈时间分别为240h、500h和1000h。或进行快速腐蚀试验方法（2h快速腐蚀相当于2000h中性盐雾试验）进行，通常6～8μm的达克罗涂层持续500h中性盐雾试验出现红锈。快速腐蚀试验是将试样浸入到75℃的20%（质量分数）的NH4NO3水溶液中。每隔15min检查一次，直至有红锈为止。 DING-RIGHT: 5.4pt; BORDER-TOP: windowtext 1pt solid; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext 1pt solid; WIDTH: 4cm; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 1pt solid; BACKGROUND-COLOR: transparent; mso-border-alt: solid windowtext .5pt" width="151"> 防护等级 DING-RIGHT: 5.4pt; BORDER-TOP: windowtext 1pt sol