I have two La Pavoni Europiccolas, 1978 and 1999. They are dramatically different machines, it seems weird to lump them together as "pre millenium". The 1978 machine normally sits as a display in my living room. (A lady from Paraguay told me that my house looks like a museum.) The 1978 machine is kept in working order, and I use it several times each month. Its portafilter is very different from the one on the 1999 machine. I normally leave brass portafilters bare because the steam causes problems with the coatings, and if I use them all the time and wipe them after each use they actually look better than when coated with protective polymers. However, the 1978 machine does not get used enough, so I was going to polish its portafilter. I decided it was easier to do this without the handle. I had thought that I had replaced the original steel threaded rod with brass. I had not!!! It was still steel, and there was serious corrosion. I soaked the area with "WD40" and eventually managed to get the steel threaded rod removed. I found some round brass stock of the right size (These use M10x1.5 threads, unlike later ones that use M12x1.75). The threads in the brass portafilter still retained all sorts of debris from the steel. There was so much debris that I could not even get the threads started! I ran a regular M10x1.5 tap into the portafilter, and then a bottoming tap of the same size to clean the threads. I made sure the threads were clean, lubricated them with a bit of grease, and reassembled the whole thing using the new brass threaded rod.

Others have had dissimilar metals corrosion damage steel threaded rods so badly that they broke off. It is extremely difficult to remove corroded steel from a brass portafilter!

I suspect that wrapping an intact steel threaded rod with "Teflon tape" would provide a lot of protection if one did not want to go to the trouble of replacing the stud. (However, when severely corroded as this one was, that is not am option.) Stainless would certainly be less bad that ordinary steel, but brass is probably best for brass portafilters.

Brass is the preferred metal here and Teflon tape cuts on the threads when assembled so you will just end up with spots of corrosion.

I have been using stainless threaded rod for portafilters for 15 years, and a viton oring as a gasket between the handle and the body. I remove the handle and rod so I can put the body in the dishwasher, every couple of weeks. I have never seen a sign of corrosion.

Either brass or stainless are worlds better here than steel, and stainless studs are quite cheap when ordered from McMaster. Brass is only available there and on eBay in meter lengths.

This morning I examined my 18 or so month old MCAL's portafilter. I discovered it was also steel. It was only slightly corroded because of the young age of the machine. I do not know if all MCAL portafilters have the same type of metal studs holding on the handle, but this one has different threads on the handle end from the brass end. The handle end is M10x1.5 and the brass end is M8x1.25.

I took a piece of brass rod and turned it down on one end and cut the M8x1.25 threads on that end and then cut the M10x1.5 threads the rest of the way.

I suggest that MCAL users frequently remove handles from these portafilters and be certain they are not corroding. Lubricate them. Consider wrapping with teflon tape. (The other option is to do as I did, but that requires a lathe or using a drill press in as a lathe.)