Too often replacing alkaline cleaners

A. You haven't mentioned the type of soils you are trying to remove or how much the cleaner bath life is reduced. If you are trying to remove oil and grease (organic soils), I would expect bath life to be shorter when running at a lower concentration. By lowering the concentration, you may be reducing the cleaner's ability to saponify the oils, thus requiring more frequent replacement. Filtration will not remove most organics; it is there to remove particulate contamination.

A. Hi Tim,

I think you may have answered your own question. If the supplier recommends to run the cleaner at 8-12 oz/gal and you're running it at 6 oz/gal, then it's no wonder that the cleaner appears to give out early.

If you need 8-12 oz/gal to get the work clean and you're running the same amount of work and the same amount of soil through the bath at 6 oz/gal, then the bath has 25-50% less active material to do the same cleaning job.

You say that your company has chosen to run the cleaner at 6 oz/gal for financial reasons. It sounds to me that this is a case of "pay me now or pay me later."

A. I hope you are not trying to remove soils common to aluminum in the same place you are removing soils common to steel. First, separate the aluminum from brass from steel. Then recognize that there is no such thing as a good aluminum cleaner (you cannot remove snot from a Kleenex !) So go to work on the SOURCE of the soil in the first place. There is no way to remove wax type, paraffin type soils from aluminum in an alkaline cleaner.

Design all you soak cleaner tanks with an overflow sump and slowly pump back into the cleaner side in a way to slowly and continuously skim the surface. Then occasionally take the floating soil out of the sump. Tell your cleaner tech service man (the salesman will not know) that you want a "separating formulation" for the soak cleaners. In over 50 years exposure to this industry and upon seeing the absolute worst oil removing problem, the cleaner change out frequency was reduced from weekly to BI-monthly by using separating formulations and an overflow sump.

Sump and skim is far more economical than filtration.

A. Hi Tim,

When you say the bath is exhausted, what exactly does that mean? Are you maintaining product concentration through regular additions? In those 2-3 weeks of use, is the work getting clean?

One possible explanation is that you have the wrong product for the job. I would expect that your chemical supplier would know which product in their range is the right one for your application, but something like unexpected soils can cause surprises sometimes.

A. Does your testing of your cleaning solution show a marked decrease in alkalinity or some other component that may be periodically boosted rather than dumping the tank?

A. Just a few thoughts on this problem. Firstly, it is unwise and not cost effective to carry out your own modifications to bespoke plating systems without doing it in conjunction with the supplier. Chemical suppliers do not give away their materials and you can be certain that what they put in is what is need to do the job properly. However, saying that, I am surprised the tanks give out so easily as even at half strength they should last more than a few weeks. I wonder is you have a leak somewhere and are unknowingly discharging the solutions to drain (or earth!?). As the volume goes down, you could be assuming the loss is evaporative and just top the tanks up with water. Alternatively, you could be losing the cleaner as drag out and again just topping the tanks with water. Either way, you will be diluting the tanks every time you top them up. The simplest way to check is to do routine (daily?) analyses of the tanks a monitor the concentrations. However, in my opinion, it is essential you follow the manufacturer's specifications and do not modify their processes as it will inevitably result in a false "cost saving" practice.

A. Hi Sachin. One of the minor memorable events of my consulting career was reading on a pollution prevention site the suggestion that the first stage soak cleaner be converted to just hot water, and passing the idea on to one of my clients who immediately implemented it. Well, you could probably safely make tea with that hot water, that's how little oil, grease and dirt came off in that first stage. It was beyond worthless.

There are two possible lessons from this. Either,
1). - it won't work, it's just a waste of time or
2). - try all ideas in the lab before committing to production.

Despite my own experience with this, I still suggest lesson 2 :-)

Luck and Regards,

A. I agree with Ted. The hot water will help a little but it could cause huge problems compared to the current process. Testing would surely be needed.

A. Put 50 ml of the cleaner solution in a 100 ml graduated cylinder. Slowly, carefully, add 50 ml of 50% sulfuric acid, stopper, invert, put on shelf overnight. Do this for a brand new solution and note the ml of organic float on top and multiply by 2. Then check your old solution the same way, subtract the above from the old, multiply by 2 - that is the "percentage of soil loading" which you take with a grain of salt until you have logged a few weeks, - then start using it as a dump or bleed/feed point.

!! As this site is used by many non-chemists who may not understand the implications, perhaps we should add to Robert's instructions.

First cool the cleaner. Add the acid very slowly and very carefully. The reaction generates significant heat, possibly enough to boil the mix. Measuring cylinders are not an easy container to mix in and are not all made of heat resisting glass. This is not what they are made for. It would be better to mix in a beaker [beakers on eBay or Amazon] and return to the cylinder after cooling.

This is one of those operations that should be done near a sink with running water and use eye protection.

Thanks Geoff! The WWW is a great advance in a thousand ways, but one of its weaknesses -- which I've commented on here dozens of times -- is that it's a giant one-room schoolhouse where people are able to see pages that are not within their "grade level". Just because we can read about something on the internet doesn't mean that we are sufficiently trained and experienced to safely and successfully undertake it.

When it comes to surgery or building airliners, untrained people seem to realize that they are not doctors or aeronautical engineers ... but people who have once made a soup or cocktail sometimes consider themselves chemists :-)

Regards,

A. Hi Sarang. There are 1001 alkaline cleaner formulations; different operating temperatures; different substrates and shapes; different soils, oils, and greases; different grease removal approaches. I think there is no way to proceed but to accumulate in-house data to guide in-house decisions on a dump schedule. But I think 6 months would be very long for most moderate to high production shops.

Regards,