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Manganese Phosphate Bath Heating and Sludge Control
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In a manganese phosphating line, we have a real problem with sludge buildup. The system is a five bath operation with stages: alkaline cleaner/rinse/manganese phosphate/rinse/flash oil. The phosphate bath sludges up quickly and must be changed often. Imersion electric heaters are used and they sludge up and burn out weekly.
Any general recopmmendations would be appreciated.
Stephen Alexander- Jacksonville, Florida
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Steve,
All phosphate baths generate some sludge. It is a pain to remove. We used a homebuilt "pooper scooper", a stainless steel dustpan with a 1" schedule 80 pvc handle. You can get quite a bit of it out after it has settled all night. It is more effective to pump it out leaving a few inches of liquid , clean it and then pump the liquid back in. It is time consuming, but periodically necessary. A pump and filter is an option, but it will use a lot of filter media and will be messy if you try to reuse the filters. Consider a bag filter.
Heaters, Go to derated heaters, yes, it takes twice as many, but it is cheaper than replacing heaters weekly. I ran used tube heaters, derated, for two years and only burned out one. Scrape, do not beat on them. They are fragile after they have been at temp once.
Protherm in California, Web is prothermco.com (I think) advertizes a flat heater that tends to crack off built up phosphate before it gets so thick that it insulates the heater and causes hot spot burn out.They say that they have had good luck with it on the west coast.
James Watts- Navarre, Florida
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Stephen:
Oh! The fun with Manganese Phosphate immersion processes. As you know quite well, sludge generation is inherent with this process. Steam heating coils are the most common source of heat for Mn Phos lines. If this is not possible, you might consider a Hydrosonic Pump made by Hydro Dynamics in Rome, GA. Hydrosonic Pump is for Mn Phos systems and is a heat source that replaces electric element and steam heat sources. This would eliminate having electric elements or steam coils immersed that would be victims of sludge build-up (scale).
Good Luck,
Bill
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Dear Stephan
Im sorry I wasn't visiting this site for a long time , otherwise I would answer you earlier .
For my opinion the problem is with your process . Your process generate to much sludge and becouse of it you have too much sludge . The right process for making good Manganesse Phoshpate is as follows:
A.Alkaline Cleaning
B.Rinse
C.Oxide Remuval with Inhibited Acid
D.Rinse
E.Grain Refining
F. Mangenesse Phosphate Coating
G. Rinse
H. Oil or Chromate Sealing .
Note: Stage E is obligative for reducing Coating Weight and Sludge formation .
If you have any more question please don't hasitate to ask
Yehuda
- Israel
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The step E is mandentory if you use an acid dip. I prefer to blast the parts, go thru a quick dip in a caustic cleaner, rinse and direct into the phosphate. It gives less problems in the phosphate step.
Working the bath as hard as you can and maintain temp (with regular chemical additions based on knowledge) gives excellent results and holds down sludge formation.
James Watts- Navarre, Florida
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Dear Sir:
Obviously tight control of the process will minimize sludge generation. Slug feeding a bath is never a good idea. Another good idea is to reduce coating weights to the lower limit. Finally, sludge generation is directly related to the difference of temperature between the heating element and the solution. As the delta T increases so does the sludge. However, in order to reduce the delta T and still maintain temperature you will need to increase the surface area of the heating element that is in contact with the solution. Lowering the delta T will minimize sludge build-up and reduce scaling on the heating element. I know it is easy to say and hard to accomplish but it will help.
Edward KonecznyBirmingham, Michigan
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