I have had the same problem when welding up a hole or slot shut on my receivers. The park comes out a different shade of gray and even the hot bluing comes out a different shade of black!
So on builds like my Tabuk where I welded on it, I just apply moly resin over the park now.
'AKSHOOTER" Black oxide is another form of Blueing . Blueing is a controlled form of rust that must be maintained when wet or very humid or you will see the red rust form. :hail: It is not as durable as Gunkote over parkerizing but as you can see , it looks very nice and BLACK !
If you are looking for something real cheap to put a complete rifle in you can use 2 plastic wallpaper trays. They are 6x6x24 but can be cut and epoxied together. I think the one I made cost about $12.00 including the epoxy.