Originally Posted by chjensen
Soldered joints failing is always due to improper technique,
This is the way to do it right and make soldered joints last.
-Use a heat shrink so the solder and flux doesn't run up the wire (under the insulation
Use good quality solder (with flux inside)
after you solder the wire - wash off all the flux residue with alchohol - this is a critical step as water+flux=acid and will corrode the wire quickly if left on.
Traditional rosin fluxes are available in non-activated (R or NC), mildly activated (RMA) and activated (RA) strengths. RA and RMA fluxes can contain a rosin that's combined with a cleaning and activating agent, usually an acid, which increases the wettability of metals to which it is applied by removing or clearing the surface of existing oxides. The residue resulting from the use of an RA or a poorly made flux labeled as "RMA flux" is and can be corrosive
and must be cleaned off the piece being soldered! This is nearly impossible with multi stranded tinned marine wire and this is why nearly all the soldered joints I've witnessed over the years are of poor quality! People use the WRONG flux or WRONG rosin cored solder!
Non-activated R or NC or a high quality RMA rosin core flux from a known and trusted manufacturer are the ONLY product that should be used in the marine environment!! There are many RMA fluxes out there that are NOT acid free...
It's your boat though so do as you wish...