Is plastic National Semiconductor (NS) TTL chips worse than others?

After the successful restore of the HP9830B I continued with the HP9810A that I was able to get from the Swedish Maritime Administration. ( http://www.datormuseum.se/computers/hewlett-packard/hp9810a ) The machine has been sitting in a storage container for many years until I was able to rescue it. And of course it was dead. Testing the CPU boards in the working 9830 gave that three out of four boards were faulty. This far I have replaced four TTL chips. Three on the clock board and one on the ALU board and all of them are made by National Semiconductor, date codes are mid 1972. All are plastic DIP. The failure mode seems to be that the outputs are floating. I guess that the bonding wires are broken. Can it be that the moisture in the storage container that has made it into the chips corroding the wires? What is the experience when it comes to different manufacturer and plastic DIP TTL? Which are better, which are worse after 40 years?