That's called a natural or business key.
In relational model database design, a natural key (also known as
business key) is a key that is formed of attributes that already exist
in the real world. For example, a US citizen's social security number
could be used as a natural key. In other words, a natural key is a
candidate key that has a logical relationship to the attributes within
that row. A natural key is sometimes called domain key.
If in your case a business key already exists and is already known as
PRODUCT_ID by the business people, a good alternative name for the surrogate I guess you want to create would be
PRODUCT_KEY doesn't look so good a name for me because the other column is also a key, a candidate key. The surrogate will be the primary a key and the natural key will have a unique index based on it, making it a business key that will be used for searches. So calling the surrogate PRODUCT_KEY would be like calling it PRODUCT_PK (slightly better).
I'd go for