Conversion coatings (phosphate layer) in surface industry

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  • Conversion coatings (phosphate) flowsheet


General flowsheet for the surface treatment of metals & plastics:


Conversion coatings (phosphate) flowsheet.jpg

Literature: BAT for the surface treatment of metals & plastics, 2006


  • Typical parameters of the process
Process Temperature [°C] Heat transfer medium Residence time Chemicals Concentration Details Literature
Alkali phosphating of aluminium 40-70 (can be lowered to 25-35 with special bath compositions) 5-10 sec Aluminium, phospahte and fluoride solutions 2-15 g/l Spraying of strip material BAT for the surface treatment of metals and plastics, August 2006
1-3 min Spraying or dipping of individuell parts
Zinc phospahting up to 95 zinc, phosphate ions and an oxidizing agent, often sodium nitrite pH: 3,2
Phosphating iron and steel 70-100 3-20 min Zn, P2O5, NO3 Zn: 14 g/l; P2O5: 9,5 g/l; NO3: 21 g/l; freies P2O5:P2=5 gesamt=0,5 OE Patenschrift, Nr. 321055, Pateninhanber: Metallgesellschaft AG in Frankfurt am Main; Gegenstand: Verfahren zur Phosportierung von Eisen und Stahl, 28.Mai 1973
Manganese phospahting 95°C continious Institut für Normung, D. DIN EN 12476 (2001).


  • Energy losses from the surface area of heated process solutions


Energy losses from the surface area of heated process solutions.jpg

LITERATURE: BAT for the Surface Treatment of Metals and Plastics, May 2005


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