I think most refrigerators have their cases and doors attracting to magnet, but their surface look like plastic plate. what are they actually made of?
Usually, a ferritic stainless steel; ferritic and martensitic steels are ferromagnetic, while austenitic stainless steels are paramagnetic to diamagnetic. Older refrigerators that corrode are probably a low alloy carbon steel, with a low level of chromium, which is used in stainless steel to provide corrosion protection. Ceramic enamel is applied to the finished steel surface, and plastic is placed on the interior with insulation in between.I think most refrigerators have their cases and doors attracting to magnet, but their surface look like plastic plate. what are they actually made of?
Probably was. We have an 'old' refrigerator that is also rusting where the enamel is cracked or pitted.I have a 1987 vintage Whirlpool that shows signs of rust where the paint is pitted.
I don't know if that is typical for that time period.
Ref: https://www.uakc.com/blog/stainless-steel-differences/here is stainless steel and then there is stainless steel. All stainless steels are not created equal. The metallurgists among us will point out that there are 5 different categories of stainless steel: martensitic, ferritic, austenitic, duplex (ferritic-austenitic), and precipitation-hardening stainless steels.
The vast majority of major appliances are made of 304 (austenitic) type stainless steel or 430 (ferritic) stainless steel. Even within these two different categories there are different grades, gauges, and finishes. Moreover, some manufacturers will use different types of stainless steel on the same appliances. For example, a dishwasher tub might have different stainless steel than the dishwasher door. Some stainless steel has superior fabrication characteristics, while others works better in specific temperature ranges, or is more corrosion resistant.