Salt in beer

I am planning on making an all grain black ipa and I am planning to add a dry rub in the last ten minutes of the boil. It has spices, brown sugar and salt. What does salt do to beer? Anything bad or just off flavor?

Sodium and chloride are fine in beer so long as they don't exceed a certain threshold. I usually put at least 75ppm sodium in all my beers, and the Cl level varies depending on style. I believe something like 250-350ppm is the recommended upper limit for Cl. So don't exceed those.

Take a look at the sodium and chloride entries in How to brew: http://howtobrew.com/section3/chapter15-1.html

I did 1/2 oz of sea salt in 5 gallons of gose and it is only slightly salty. The recipe in Brewing with Wheat calls for ~1/2 per gallon, I tried that scaled to a glass and it was way too much for me.

It will be a very small amount about 1 maybe 2 teaspoons of the rub my objective is to bring some heat to the overall flavor of the beer. This rub has some good hot spices to it!

Gose is the only style that routinely uses elevated sodium and chloride content from added table salt. It is a unique soured beer that can meld that flavor within its sour profile. I've had a professional brewer with an award winning Gose provide me with the amount of salt they add to their beer and it ends up delivering on the order of 250 ppm sodium. That is pretty high.

More typical beers with more moderate pH are not going to meld that flavor very well. Keeping sodium below 100 ppm is typically going to be a good flavor benefit.

With this rub, there is no telling how much sodium or chloride you're adding. I'd go easy on the addition. You might want to test out how much salt added to your total batch would bump your concentrations using a program such as Bru'n Water.