What is the surface of fridge door made from?

[kenny1999]

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?

 

[Borek]

Most likely sheet metal with powder coating.

 

[hutchphd]

Typically the outer shell is steel (stamped in a press) and the inner shell is a thermoset plastic, either vacuum or press formed. In between is insulation. I just spent the morning in my freezer. It is feeling better now.

 

[russ_watters]

I just spent the morning in my freezer. It is feeling better now.

But how do you feel? Cold?

 

[hutchphd]

Sore. Its a bottom freezer and I am officially old. But the ice cream feels cold

 

[Astronuc]

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.

 

[rbelli1]

Older refrigerators that corrode

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.

BoB

 

[Astronuc]

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.

Probably was. We have an 'old' refrigerator that is also rusting where the enamel is cracked or pitted.

I have a paper somewhere that describes steels used in appliances, but I can't readily find it.

Here is an example:

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.

Ref: https://www.uakc.com/blog/stainless-steel-differences/
304 is perhaps the most common commercial austenitic stainless steel, which can be mildly magnetic if it contains some ferrite or martensite (depends on forming method and heat treatments). I have seen 430 (ferritic) referenced with respect to appliances, and it is ferromagnetic.

Another example - https://millsproducts.com/grades-metal-appliance-stainless-steel-handle/
https://www.steel.org/steel-markets/appliances/

Stainless steels need a certain level of chromium (typically at least 13% and up to 22%) to maintain the protective Cr₂O₃ layer on the surface. Chromium is a ferrite stabilizer and will promote a ferrite (bcc) microstructure in the steel. Nickel and manganese are austenite (fcc) stabilizers and will promote the austenite (fcc) microstructure. The 300 series austenitic stainless steels of which 304 and 316 are the most common contain about 18% Cr and 12% Ni. Original versions of 304 were called 18/8 or 18-8 stainless steel, with a minimum of 18% Cr and 8% Ni; the Ni was rather low, and it more like 11-12% these days. Stainless steel 316 contains about 2.5 +/- 0.5 wt% Mo, which enhances the effect of the chromium in protecting the stainless steel.

The 400 series stainless steels are ferritic or martensitic of which 430 and 440 are common. Ferritic stainless steels like 430 have about 16-18% Cr, about 1% Mn and no Ni. Martenitic stainless steels have a little Ni, typically around 1%, but few have more. Low-Ni or Ni-free stainless are preferred for cooking, especially acidic foods, because Ni leaches out of steels and some folks have allergic reactions to Ni.

Sometimes Mn and N are used to offset the lack of Ni. The 200 series stainless steels fall in this category.