Thread corrosion on 1960s Tech top cap.

[polod]

I noticed that the majority of 1932 Tech razor's heads are made of solid brass, with chrome plating. The threads on the top cap never corrode. However, I noticed that the later Tech razors, mostly the ones made during the 1960s (the ones with the Gillette logo embossed into the top cap) the threaded posts seem to corrode. Usually there in a black gray looking corrosion on the threads and in many areas the threads are broken and flaking off in small pieces. I've come to the conclusion that the later techs, the top cap piece is not made of brass, but some other metal, does anybody know? It's a shame too because I have a lot of later tech models with corrosion on the post, but nowhere else. Like I said before, the earlier techs didn't have this problem. They must have changed the metal composition. Attachment is the 1960s tech on the left that seems to have this corrosion problem. The right picture is the older style 1932 Tech razor that is free of the corrosion problem on the top cap threaded post.

 

[Greybeard]

The top plate is made of zinc/zamak. Zinc is difficult to plate and corrodes quickly. The top plates themselves may have issues with blistering and pitting. Screwing the handle onto the head strips the threads of the chrome plating that prevents corrosion. Zinc oxide is dark grey and powdery.

All the beveled Tech head top plates and some of the later logo'd models are zinc. Strangely enough the bottom plates are mostly brass, regardless of the top plate material.

 

[cooncatbob]

The top plate is made of zinc/zamak. Zinc is difficult to plate and corrodes quickly. The top plates themselves may have issues with blistering and pitting. Screwing the handle onto the head strips the threads of the chrome plating that prevents corrosion. Zinc oxide is dark grey and powdery.

All the beveled Tech head top plates and some of the later logo'd models are zinc. Strangely enough the bottom plates are mostly brass, regardless of the top plate material.

The caps are cast, the base plates are stamped from from sheet stock which is why they're still made from brass.
Zinc melts at about 800 degrees, brass at about 1600 degrees so zinc is easier and cheaper to cast.
I've also found that some but not all of the Tech caps with the frosted Gillette logo are made of Zinc, best way to tell is by weight, a zinc cap weighs about 2/3rd what a brass or copper cap weights.
The zinc caps weigh 10-11 grams and the brass/copper caps 14-16 grams.