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topic 591

Seeking biodegradable stainless steel cleaner


(1996)

We are pleased to write to you for the above information. We are currently looking for a biodegradable stainless steel cleaner. As you know well, conventional cleaner is a chloride which is very corrosive & toxic, and environment activists have the power so that we cannot use this compound any more. Based on our test biodegradable strong acid could not clean as shining as we want. If you know something powerful cleaner, please let us know.

Your kind assistance would be greatly appreciated.

Y. W. Park
Kwanak Gu- Seoul Korea


(1996)

The cleaner selected depends on the soils present. Generally speaking organics i.e. oil, grease, Metal working fluids, are cleaned with alkaline cleaners. Inorganics i.e. Tarnish, oxides, scale are removed by acids. I would need to know the soils you are looking to remove.

In respect to "biodegradeable" it deals specifically to the surfactants. The cleaner could contain other "bad actors" but be biodegradeable. Interesting to note in discharge situations the cleaner could be OK but the soils could contain the "bad actors."

An example would be a chlorinated soluble oil used as a coolant with some metal fines.
Please let me know more specifically what your discharge requirements are so that I can assist in the recommendation.

Dan Zinman



Citranox

(1996)

You will find a lot of cleaners if you contact the regular metal finishing suppliers. I am sure companies like Technic, LeaRonal, and McGean-Rohco have international distribution. Biodegradable is another problem. One you can try is from the Alconox Corporation, called Citranox [linked by editor to product info at Amazon], which is a citric acid solution plus a wetter. I think it is biodegradable. Contact any laboratory equipment/chemical supplier.

bill vins
Bill Vins
microwave & cable assemblies
Mesa (what a place-a), Arizona 


(1998)

As manufacturer of CITRANOX, I was pleased to see the recommendation from Bill Vins - thanks Bill. The recommendation is correct.

Bill is absolutely correct, a good acid metal brightening cleaner should give you the results you are looking for.

Malcolm McLaughlin



(1998)

Our industry lives in a world of "patent medicine", as described by Langford and Parker in "Analysis of Electroplating and Related Solutions" [linked by editor to info about book at AbeBooks]. For reasons which I can only imagine, they elected to leave a 1961 discussion on the compounding of cleaners out of their newer edition.

So, I really did not know that chlorides are a major constituent of cleaners for stainless steel, and never thought of chlorides as toxic.However, in a review of my vast library (8 books), I found that fuming nitric acid/sodium chloride dips were used to clean Monel (67 Ni, 30 Cu, 1.4 Fe, 1.0 Mn, 0.15C) but not Inconel (80 Ni, 14 Cr, 6 Fe), due to the high affinity chromium has for oxygen. One formula I found for the removal of oxide films on Inconel is an alkaline potassium permanganate bath followed by a sulfuric acid, sodium nitrate, copper sulfate solution.

I would like to know if the original letter is related to cleaning; removal of surface soil, or to pickling; removal of oxide film or scale, according to

M2O + 2 HX yields MX2 + H2O

Since the alloy is so important in the successful cleaning operation, I think it important that we know what alloy Y.W. Park is treating.

What is the reaction when using acid cleaners? What would be a good definition of biodegradable? Are chelating agents present in all acid cleaners? Acid cleaners remove oxides, right? How about scale? -tom

tom pullizzi monitor
Tom Pullizzi
Falls Township,
   Pennsylvania 


(1998)

To answer one of your questions, Tom... Citric Acid is a chelater in the purist sense. It holds onto metals as tight as anything does. These new citric acid passivates must be handled with extreme care when waste treating...not mixed with other waste streams or your treatment costs and time will skyrocket.

Mike McDonald
mack products - Jefferson, Wisconsin


(1998)

Does the original letter mean a molten salt bath when it refers to a chloride? That would explain the toxic characteristic. Or the "chloride" might be a fluoride, since I found a formula using nitric & HF for stainless steel.


Tom Pullizzi
Falls Township, Pennsylvania

(1998)

Stainless steels are protected by a passive layer of Chromium oxide at the surface. Acid cleaners containing any Halogen (Fluoride, Chloride) attack this protective layer. Eventually they cause pitting to occur. Chloride ion is a reasonable complexing ligand used in many metal complexes such as Chloroplatinic Acid or Nickel Chloride which is the basis for Wood's Nickel Strike.

Many chelators can be broken by UV light. A company in Canada produces UV light systems to break these chemicals down so that Hydroxide precipitation can help remove the metals from the water. All chelators are potential problems to your water treatment system.

Dave Fairbourn
Sandy, Utah



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