这个生锈的叫mounting ring, 是和sink连接的挂件。一般用螺丝刀把三个bolts松下会自动pop up and loose. 如果生锈的话,可以试试:(googled)
A stuck garbage disposal mounting ring can be removed by turning it counterclockwise and applying pressure, especially if the sink flange is also stuck. You can use a wrench or a screwdriver to rotate the ring, and applying penetrating oil like PB Blaster can help loosen it if it's rusted. If the sink flange is stuck, you may need to heat it with a heat gun or use a hammer to loosen it.