question about copper lines in refrigerators

The amount of copper tubing outside the compressor, that you can get to by hand, isn't much.

It adds up, but it takes quite a few fridges, I do it as I remove the compressors anyway.
Watch where the copper tube is joined to the steel tubing, you will notice a couple of silver welds there.
Use a magnet to check the different tubing materials.

Because you cannot weld Ali tube to Copper tube, or Steel tube to Ali tube.
The engineers use 'joiners' made of a friction welded Ali/steel, or Ali/copper tubing. They then weld these connections into the tubing lines in the factory or wherever they work on the fridge/freezers.

Most fridges are different but all combine the Ali~Copper~steel tubing ideas.

Some use copper tubing all thru the fridge or freezer, common with old fridges, ie pre 1970.
Often they used brass or copper liners in the inner fridge/freezer condenser cooling surfaces back then too, it always pay to check.
My God it pays......$$$$ anything up to NZ$50+ for one fridge!!

Later ones use steel tubing from the compressor up to the condenser & more modern ones, its Ali tubing & a Ali condenser surface, easy to see, its a sheet Ali with lines embedded & running across the surface, normally they are painted white.
I rip these out & flatten them & save them up, you need to cut the 2 small steel tubes out where the welds are. They don't take up much space that way & fit well into a plastic sack.
Use a magnet to check where they are..

Sometimes the Ali tubing has a fine copper tubing running thru it, I bend the Ali tube a little back & forth & often it breaks & the copper tube is still joined, if the Ali tube is unkinked you can pull the fine copper tube out.

In freezers, theres the tubing running inside the top end of the sides of the freezer, thats the condensing surface.
Sometimes its copper tubing, more often I find its just steel tubing, you need to check it physically as often the copper tube is held in place by a bunch of thin metal plates before they 'blow' the insulation into the freezer walls.
So, just by checking it with a magnet, you can be wrong.

Real modern fridges, later than yr2000 & often a 'frostless' sort, use a Ali fin condenser with fans to move the cold air around.
I would first check the circuit boards on these as often its just a blown circuit board anyway, it'd possibly be worth repairing.
-----

Basically, check what you can get to with a magnet, if it dosen't stick, its either Ali or Copper.

If its a old fridge, check the lining to see if its magnetic or not. If it isn't magnetic, or plastic, scratch & check it to see if its copper or brass, often its painted blue or silver.

If its a older freezer, check inside the walls to make sure its not copper tube lined.
You can break thru the top surface edge with a crowbar & lever some of the tubing out to check it.
Real old fridge/freezers are normally filled with polystyrene & tar, a pain to get around.

On modern (1970~2000) fridges, some of the tubing that runs from the compressor up inside the fridge walls is copper tube, thats the stuff thats probaly not worth getting, you need to rip open the walls & its filled with that tan coloured 'blown foam' material.
If theres a long, white painted tube running up the outside of the fridge up to the top, its probably Ali & with the fine copper tube inside it.

I just cut the tubes where it meets the lining, if theres a very thin copper tube there as well, you can grab that & pull most of it out, often that thin copper tube is welded to the copper 'sausage like' drier unit.

That 'sausage like' drier has a silver weld at each end, inside it is two metal filters & a 1/2 handfull of drier material, it looks like white ceramic balls, its useless.
The filters/sieves are either steel (brass coated) or brass, you have to remove this before you sell it.
I save up 10 or so & do them all at the same time. The copper weighs about 50grams(?).

I use garden tree branch loppers, lop each silver welded end off, lop close to where the sieves are & pour out the drier material, then lop sideways thru the sieves & pop them out of the thin copper wall.

A picture is worth a thousand words, hope you get the picture