Chemical Electric Etching issues

What fluid is used to carry out the etching, and at what temperature and pressure?

It is not a very high tech process.

A controlled-depth, permanently etched mark

of any design or detail is made by the operator

on metal surfaces in a matter of seconds. It is

simply made by placing the MARKING

APPLICATOR over the STENCIL in

contact with the PART to be marked. The

part is positioned on a GROUND PLATE to

complete the electrical circuit. The current and

the electrolyte fluid do the rest. The

result is a permanent mark which can only be

removed by buffing or grinding the metal down

to the depth of the mark. Occasional blotting

of the applicator and stencil in the STENCIL

CLEANER TRAY replenishes the electrolyte

supply and helps to keep the stencil apertures

clean.

My concern is that it affects the tubes substantially enough to possibly cause a failure in the future. These tubes are high pressure.

Your "concern is that it affects the tubes substantially enough to possibly cause a failure in the future. These tubes are high pressure." is appropriate, however, the design and regular testing of high pressure tubes will detect any problem before a catastrophic failure.

Any pitting is not a problem until it has compromised 25% of the wall thickness. At this percentage it will be at minimum standard to probably fail an overpressure test, which is considerably higher then the operating pressure.

It is good to be proactive, and prevent future failures, I wish that everyone was as conscientious as you.

If the pitting is close to this depth, you may want to consider a different source of your marking supplies, or evaluate whether the procedures are followed as per instructions.

Techno, all very good points. This verifies my thoughts.

Testing and inspection at time of production indicate good tubes. The idea is that these tubes could sit on the shelf for years before being applied. External surface corrosion would be evident however internal would not be.

If I were to scale the safety rating of the application from 1 to 10 it would be a 10.

ah a 10.

In that case, during regular maintenance periods, the tubes are ex-rayed which will detect even internal flaws.

It would be prudent to have a sample of your tubes tested in the stamp area by a metallurgist.

"It would be prudent to have a sample of your tubes tested in the stamp area by a metallurgist."

Exactly my recommendation. Which fell on deaf ears. But I am still trying.

Not deaf ears, just tight pockets. Think of who you are talking to. Unless a problem has been identified by the end user, or your quality has significantly changed from earlier processes; it is understandable that the boss is unwilling to spend extra money. His goal is to make a profit with the least cost.

Unless it will make him more money, he will not even consider it. Consider if he did the test. Bad results will cost him money to change his process; a process that is apparently working OK now. It will also identify his product as inferior - not good for business. The only way a good result could make him money is if he could identify his product as superior to a competitor's product. Has there ever been a report of a competitors product failing in the stamp area?

The only problem is your approach. You have falsely assumed his concern for quality is for safety of the end user. It is more likely that he is concerned for standards and product rejection that will cost the company $$$. He may have used the safety line to encourage the workers to keep the standards up. Apparently it worked too well for you.

Just like a speech you have to consider the audience. If you make your presentation so that the boss will look good, or you will save the company money, and use the safety factor to hide the bosses greed, they might consider it. Always give them three options, so it would be their decision. The first option would be the ideal and most expensive. The second option would be the realistic option, and the third option would be the cheapest and unacceptable option. 90 percent of the time they will go for 75% of option 2 and 25% of option 3. This makes them the owner of the decision. They are usually unaware you set them up, as your presentation is obviously the cumulation of your work.

Instead of fighting the bosses and confronting him, change your presentation so it is appearing that you are working for them and not the customers.

Good luck

I certainly wish I could go into more detail. I can say that my approach has been one of facts and options. I am not one to enter the boxing ring with my findings. And I rarely make assumptions.

The $ issue is always a stong one. That's the purpose of most business. In this case the risk and liability has far outweighed the process and product cost. It was just a matter of getting management to move on it. I believe we are there now. I know it's a tough matter on their end dealing with the customer and the CYA factor.

There are two problems here:

1 Electricity; In my experience, anywhere electricity is passed, the molecular, and chemical structure is modified. Since there is some arcing, though small, some micro pitting or molecular modification may occur. To minimize this, the heads must be clean and polished smooth. Any distortions will cause arcing to occur always in the same place and concentrate the effects.

An easily visible example molecular change is; the first place a metal will rust is at the edge of an arc weld.

2. Chemical etching. My wife business is working with metal patinas. Regardless of the manufacturers claims, any chemical residue will continue to patina, or oxidize the metal for years after the process. We have found that the best defence is to thoroughly rinse the area with water to neutralize as much of the acid as possible, dry, and then coat with a water based lacquer. The ink is designed to etch your metal only as deep as the mark. Again if the heads are dirty, excess ink concentrated in specific areas will leave residue that will eventually etch small pits in the metal.

There is the other possibility is that the ink is not properly mixed to an even concentration, as in some aftermarket inks.

There is a definite issue with using this type of process in marking product. Testing and further review has confirmed this.

The many parameters involved in this process makes it difficult to control in our application.