The "plate" is a SS box, with a coil inside. The R134a circulates through it in a copper pipe, after passing through the expansion valve.

Of couse I will have to refill the plate once it is leaking no more. There is salt water in the plate, perhaps with some corrosion inhibitors It is easy to calculate a suitable salt concentration

I wonder what, if any corrosion inhibitors would be useful

Most Importantly for the temporary repair, how to seal the leak of eutectic?