And only one class the Alfa fast attack submarine the titanium hull was used more to reduce weight (Half the displacement of a comparable Los Angeles class US attack submarine) to allow it to be the fastest submarine ever constructed (double the reported speed of US attack submarines and most likely at least 25% faster than their actual speed) rather than because titanium is non-magnetic.
All Alfa subs were decommissioned in 1990 and sold as scrap.