So to the question in hand about the shelf life of plumbing flux, my tub was over 2 years beyond the expiry date. The effect of the flux is very similar to the way washing up liquid reacts in the washing up bowl as it dissolves greasy food when washing up dirty pots and pans.īasically the wetting agent mixes with the dirt and any oils on the metal surface, dissolving them making them easier to remove The acidic compound within the Flux and is also known as the activator, this part of the compound converts the oxides into soluble metal salts and cleans the surfaces of the joint and removes the oxides. The ingredients that make up the wetting agent of the flux are called the surfactant and allows the flux and solder to flow over the surfaces and create a good bond that will not only be strong it will also be conductive. If the flux does not flow it may form a bad joint often called a ‘Dry Joint’ This and allows the solder to flow between the surfaces and creates a good, clean joint also known as “wet joint”. The acid within the flux cleans metal surfaces and reacts with the oxide layer, this leaves the surface primed and enables a good joint. Surface oxidization takes place constantly when the surface is exposed to any oxygen in the atmosphere but the process increases when soldering, due to the higher temperatures. When it is melted, the applied flux spreads out over the metal surfaces to be joined and cleans off particles of dirt and creates a barrier to the atmosphere which prevents any oxide layers from forming.
#Tinning flux free#
A solder joint bonds two compatible metals with a soft metal bonding agent called solder, this requires compatible materials and clean metal surfaces that are free of dirt and oxides, that can prevent a good bond.įlux is applied with a brush to the parts to be joined and the areas that will form the bond.
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