What's the best N connectors for LM600 ultraflex cable. I had SWR
problems with one antenna that I troubleshot to the connector. Crimp
was corroded and plating peeling off. Checked two other cables I had
installed while they still seeemed electrically sound the corrosion
was also present. Antennas had been well sealed and no detectable
moisture inside. Even the ends in the shack were gunked. Help on this
would be much appreciated.

KD4RQE
Jimmie

You just might have galvanic corrosion of two dissimilar metals.
There is some chart that shows the metals in a list, the metals close to one another will present no problems, the metals farther apart will perhaps have problems.

Aluminum and brass are two metals that will corrode [in the presence of moisture]

Plus the plating that you spoke about... do you really knows its composition?

I would go with a different brand of connector , perhaps more expensive..

Perhaps calling the manufacturer of this coax and ask their recommendation