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What is Flux Used for in Plumbing?

If you’re an avid plumbing enthusiast or even if you just like to keep up to speed with DIY, you’ve probably heard about something known as flux. This is the one product in a plumbing and gas professional’s toolbox that is used virtually every day and that is impossible to live and work without. The material itself has been used for well over 100 years and will no doubt be in regular use for many more years to come.

Flux technology has seen rapid improvements and changes in the past years. Taking this into account, let’s take a look at the product that millions of plumbers take for granted but that’s completely essential.

So, What is Flux Used For?

A good quality flux should always be used and will perform three main functions:

  • To clean metal surfaces to make sure of good solder flow
  • To protect the surface from recontamination
  • To promote the flow of solder around the joint

As you may have already guessed, the actual word ‘flux’ means flowing or to flow. This is one of the major aims of a great quality flux – to aid the solder to ‘flow’ around a fitting as it is sweated to the tube or pipe. The flux can do this by doing all of the above. So, let’s take a closer look at what this actually means in depth.

Dirt and oxides are removed at high temperatures by the flux, showing a clean and fresh surface for the solder to bond with. Additionally, the flux stops the newly created surface from becoming re-contaminated. Another great thing is that the flux actually controls the surface tension of the metal surface as well as the molten solder to draw it along. If there wasn’t flux performing these three critical tasks when soldering is carried out, the molten solder would just drip off without any bonding at all. To see for yourself, why not have a go at soldering without flux and see what happens!

What Forms Does Flux Come In?

There are two basic forms that flux comes in – paste and liquid. Acid-based paste fluxes tend to be applied with a brush and are usually used for piping, plumbing and other applications that call for larger quantities of flux to be used before soldering. These are also soluble in water so are easy to clean up just using good old-fashioned water and a rag. It’s the acid in the flux that attracts the solder material into the joint created by fittings joining together. As the solder is drawn deeper into the joint, the entire gap is filled, creating a tight bond. Liquid fluxes are generally used for intricate and small parts.

Types of Flux Explained

Ask any plumber Perth-wide about types of flux and he’ll have lots to tell you. The thing is though that the underlying chemistries of different types of flux can be pretty complicated, so there’s no point getting into that! Generally speaking, there are just a few basic categories of flux. When you know the weaknesses and strengths of each type, you can then choose the right one for your job.

1. Water Soluble Flux

Water soluble flux is great for heaps of jobs. This general-purpose flux is useful for so many different types of solders and metals. The flux itself tends to have an elevated content of active ingredients so it’s great at cleaning metal as well as at surface tension control for better solder flow. One thing we would say is that these fluxes can char pretty easily and can potentially cause surface discolouration. Thankfully, however, this discolouration can be easily removed and will not affect the metal negatively. Also, as these fluxes are soluble in water, any remnants left are rinsed away easily after soldering. Taking all of this into account, the best use in terms of this kind of flux is in terms of good rinsing capabilities and for top class solder spreading.

2. Petroleum-based Flux

Petroleum-based (also known as Petrolatum) Flux is a general-purpose flux that’s petroleum-based (as the name suggests!) This flux usually contains the highest available levels of active ingredients. It also tends to be more acidic so could cause more of an environmental hazard. In addition, petroleum fluxes are notoriously resistant to burn-off and also to over-heating. That’s great, however, they’re not wildly effective at promoting the flow of solder. Also, the grease in these types of fluxes means that residue is exceedingly difficult to flush with water. All things considered; this flux is best for your project if you’re looking for additional heat resistance.

3. ASTM B-813 Compliant Flux

This specific type of flux is both water-soluble and less corrosive. These letters and numbers refer to a standard that relates specifically to copper plumbing and that specifies the functionality of the flux. How these fluxes maintain the status of being less corrosive is by having lower levels of active ingredients. What you then need to bear in mind with these is that the solder flow and the cleaning ability might not be as great as it is with other fluxes. Another negative is that they’re susceptible to charring but, on the other hand, any residue will rinse away naturally. The bottom line with this flux is that it should be used if this particular standard is enforced in your area.

4. Speciality Flux

Lastly, we are going to look at speciality fluxes that are designed for exotic solder/metal combinations. These can include silver, aluminium and stainless-steel solder and, of course, are used with the specific material you are working with.

So, there you have it, the lowdown on all different types of flux and their uses from the plumbing services Perth professionals at Baywood Plumbing & Gas. We know all there is to about all kinds of residential, commercial and business plumbing, so we can pass on our knowledge and savings on to you, our customers. Just get in touch for a quote at a time that’s convenient to you.

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