I have made a picture/art frame from some mild steel angle 40mm x 40mm 3mm. Mitred the corners and then mig welded the pieces together. Then I've give it a go over with a grinder and flap wheel. I was surprised how it started to buff up and shine. I really wanted it rustic/rusty looking so I've give it a splash of vinegar and left it outside in garden. Already its started to rust and gain some patina. I want to seal in the rust /patina so was going to leave it outside in the weather for a week then bring it in and let it dry and then seal it with some lacquer. I normally only spray water based paints due to ease of washing out and fumes and drying. I have some water based floor varnish so was going to spray it with that until it's got a good build up and then see what happens? I know I should be using a spirit based lacquer but all I'm trying to do is seal in the rust and in the end after multiple coats it will be sealed from the elements. The picture frame will be used in doors. Any thoughts?