Conversion coatings (phosphate layer) in surface industry

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• Description of the process

• Conversion coatings (phosphate) flowsheet

General flowsheet for the surface treatment of metals & plastics:

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

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

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