Here's a different slant...
I'm not sure where you were, but I'm thinking that it may not be the sink... maybe it was the water itself.
Out here in AZ, the water has a VERY high alkali content... and it leaves a film on everything it contacts. Sinks, shower walls, drinking glasses... everything. This is the only place I've ever been where you HAVE to chamois your vehicle after you wash it, or else it will look WORSE than it did beforehand.
No one here drinks it... there are water filtering outlets everywhere to take your 5-gal bottles for refilling.
The locals here have various methods for 'descaling' it... orange & lemon zest mixed with vinegar, CLR, Kaboom, etc...
Bottom line... all I'm saying is that, maybe there's nothing wrong with the sink.
2013 VOLTAGE 3200 (EPIC I & II)
2014 Ford F-450 PLATINUM