Copper Pipe Bright Dip

Question:

We manufacture copper piping components that have attachments soldered, brazed and silver soldered in and on the tubes. I have two items that I need some help with:

We currently use a concentrated vinegar solution to clean the joints made with either 18T, 45T or Blockade. It works pretty well for us and is more environmentally friendly than other cleaners. Is there a better method we should consider?
We have been asked to manufacture a product that has a bright dip specification. We neither use nor are we set up for the kinds of chemicals required for the bright dip solution. Is there an alternative to sulfuric and hydrochloric acids? C.H.

Answer:

In answer to question 1, I am not familiar with the products mentioned, but will assume that they are fluxes considering you are soldering and brazing copper pipe. The “active” component in vinegar is acetic acid, which does most of the flux removal from the brazed and soldered joints. Your possible alternatives can range from one end of the spectrum to the other as far as aggressiveness and effectiveness are concerned.

In general, you may be able to remove a significant amount of the flux with a warm water quench immediately following the brazing or soldering. The change in temperature will be enough to “shock” most of the flux from the part. Any remaining flux may be removed simply in a hot water soak. For this to work, it will be important to process parts relatively quickly. Obviously, quenching will have to be done immediately following brazing. The sooner the hot water soak can be done, the easier it will be to remove the flux residue. The other end of the spectrum would be a cleaning step with something more aggressive like sulfuric acid. Due to the strength of this acid, parts could sit around longer between brazing and cleaning with less effect on the success of the cleaning. Although more aggressive, the sulfuric acid can present its own problems from the standpoint of worker safety and waste treatment.

Regarding question 2, the bright dips I am aware of are all based on one or more mineral acids, some with additives to increase the reaction rate. You would have to probe more deeply into the needs of the customer to see why it is specifying a process like this.

A general compromise in both areas would be to use citric acid. It should do as effective a job in flux removal from your parts, especially if used with the quench mentioned above. While it would not be as effective as a bright dip, it would also generally brighten the copper and remove some of the heat tint and oxide from the soldering or brazing operation. Finally, you must be getting some objections from the workers in the area of the vinegar because of the smell. The citric acid would eliminate the odor problem as well.