CHEMFIX 7
( Refiner before
Zinc phosphating )
INTRODUCTION
‘ CHEMFIX 7 ‘ is SURFACE CONDITIONER which activates and prepares the ferrous metal surface to take a tightly adherent, fine & smooth zinc phosphate coating. When certain steel surfaces are cleaned with either acid or alkali prior to phosphate coating, coarse & sparkly coatings may develop. However, dipping the work in ‘ CHEMFIX 7 ‘ bath prior to phosphating will prevent this effect. The phosphate coating which forms on a steel surface after ‘ CHEMFIX 7 ‘ treatment is uniform, dense, adherent and of smooth texture.
OPERATING DATA
‘ CHEMFIX’ BATH MKE – UP
For each 100 litres of bath, add to water with stirring
‘ CHEMFIX 7 ‘- 0.5 kg
CONTROL POINTS
BATH TEMPERTURE - Room temperature
DIP TIME- 30 seconds to 1.5 mts ( Max )
TITRE- 7 to 9 ml
pH-1.5 – 3.0
… P 2
2
PROCESS SEQUENCE
Treatment of work in the ‘ CHEMFIX 7 ‘ bath immediately follows cleaning and rinsing and immediately precedes phosphate coating. The normal process sequence including ‘ CHEMFIX 7 ‘ treatments, is therefore, as follows :
Stage No.1-Precleaning, acid or alkali
Stage No.2-Rinsing
Stage No.3-Chemfix 7 treatment
Stage No.4-Phosphate coating
Stage No.5-Rinsing
Stage No.6-Passivation
PRECLEANING :
‘ CHEMFIX 7 ’ is a surface conditioner not a cleaner. It is effective only on surfaces which are free from oil, grease or heavy rust.
CONDITIONING WITH CHEMFIX 7
The cleansed work is treated in the ‘ CHEMFIX 7 ’ solution for 0.5 to 1.5 minutes at room temperature and immediately transferred to the phosphating bath without any rinse in between.
NOTE :
An immersion time of 3 mts or longer may actually impair the rust inhibiting and paintbonding properties of the subsequent phosphate coating.
After ‘ CHEMFIX 7 ‘ treatment, the work must NOT be allowed to dry.
‘ CHEMFIX 7 ’ should not be usedbefore phosphating in a zinc – calcium bath like that of CHEMPHOS 20
… P 3
3
MAINTENANCE OF THE BATH :
The ‘ CHEMFIX 7 ‘ bath is controlled in the plant by a single titration.
Pipette 10 mls of bath solution into a beaker and add a few drops of phenolphthalein indicator solution. Titrate with 0.1 N sodium hydroxide until a faint pink color appears. The Titre should be between 7 – 9 ml
REPLENISHEMENT
For each ml below 7 add 70 gm of ‘ CHEMFIX 7 ‘ per 100 litre bath to raise the Titre by one.
pH 1.5 – 3.0
Check the pH with a pH paper. If the pH is lower then 1.5 add fresh demin water to raise the pH within the range of 1.5 – 3.0
EQUIPMENT NOTES
‘ CHEMFIX7 ‘ is mildly acidic and the bath can be contained in a mild steel tank.
SAFETY PRECAUTION :
‘ CHEMFIX 7 ‘ is a poisonous chemical. Operatorshould use gloves when handling it. They should also wash thoroughly their hands before taking any meal.
FURTHER INFORMATION
For further information on chemical processes for pretreatment of metal surfaces and prevention of corrosion apply to the following .
CHENNAI OFFICE:THIN-CHEMIE FORMULATIONS
‘ BEJOYA ‘
30 School View Road
Chennai 600 028
Phone : 2493 8148
Fax No: 2495 4012, 2496 0657
Email :
****************