Aluminum Group EA335 Chair Restoration  

I’m new to the forum and have an aluminum group desk chair (EA355 per the underside label, circa 1989) that has been making an increasingly pronounced creaking noise when shifting seating positions. I’ve just traced it to a crack in the horizontal tube that connects the tilt mechanism to the diagonal bracket on one side of the chair (see photo below). The weld is intact—the crack is in the tube itself and runs along the length of the weld and then turns perpendicular to it. Does anyone know a source for a replacement assembly (I’m in the US)? Given the size of the crack, I have to think it will fail completely at some point.

Also, there is substantial wear and deep scratching on the arms. Are these components solid, monolithic cast aluminum, or is it a plating over a core material (presumably both aluminum)? There is a bit of a ‘edge’ at the wear points that makes it seem like a plating.

Thanks!