Know a plumber? Know an electrician? They know about solder, but most people don’t.There are all different types of solder, used for a wide variety of applications and even some multi-applications. It’s confusing when you see so many choices that all appear to be the same thing. Let’s clear some of that up.
Rosin core, acid core, flux core, lead solder, lead free, 60/40 tin, low temp, high temp: These are all the different terminologies when choosing solder. Ask a plumber “What kind of solder do I use?” and he’ll say “What do you want to do?” Ask an electrician “What kind of solder do you use?” he’ll say “Depends on what you want to do.”
Here in the starter and alternator world it’s pretty safe to say we basically work on passenger cars and trucks. Starter and alternator shops use a lot of solder in different ways. Sometimes we use acid core if the job is really dirty, and large enough that corrosion wouldn’t be a factor later. The solder of our choice that would be mostly used for many automotive electrical applications is rosin core 60/40.
(60/40 means 60% tin, 40% lead). Lead free solders are needed for plumbing, but most experienced solder personnel feel that lead is easier to apply and provides a stronger bond after drying. This is not an advertisement, simply a fact, in our shop, over the years, we have found the brand name Kester to be readily available and seems to have good dependable results and flow.
Let’s study solder for a moment on the molecular level. The presence of oxidation is in direct relationship with a poor solder joint. This presents a problem because heating the metal to a high enough temperature to liquefy, causes intense oxidation. This is why flux is used. Flux provides a coating on the metal, so it will resist oxidation while being heated.
So, for general purposes around the starter, alternator shop, you’re going to see a lot of 60/40 rosin core. It’s just the best choice for what we want to do.