FREIBOND D31 is a high quality low temperature iron phosphate coating chemical for steel primarily applied by spray.
FREIBOND D31 is designed to both clean the substrate surface and simultaneously impart a uniform coating excellent for bonding paint. The cleaner package in FREIBOND D31 is formulated with special fast acting surfactants to provide quick removal of light surface soils while preventing redeposition allowing more time for the phosphating reactions.
FREIBOND D31 may also be used by immersion but at double the recommended concentration.
Stainless steel, mild steel, and high temperature acid resistant plastics are suitable for processing equipment. Full cone spray nozzles, such as Spraying Systems WhirlJet® nozzles, are normally used in spray applications to ensure uniform application of FREIBOND D31. Spray pressures should be maintained between 15 and 20 psig. Spray pressure above 20 psig will create inconsistencies and voids in the iron phosphate coating.
To charge the tank, fill to the three-quarter level with water and for each 1000 gallons of working solution; add 410 lbs (40 gallons) of FREIBOND D31 and 8 lbs of NEUTRALIZER 1. Bring the tank up to the working level with water and heat to the operating temperature, from 80°F – 160°F. Once the optimum temperature determined, it should be maintained within 5°F. A processing bath built up according to these recommendations will result in 11.5 points of Total Acid and a pH adjustment value of 0.4 (pH of 5.0).
An appropriate Freiclean product followed by a rinse stage can precede FREIBOND D31 cleaner/phosphating application, but is not required. If a supplementary cleaner is used ahead of the FREIBOND D31 the rinse stage ahead of the FREIBOND D31 can be adjusted with ADDITIVE 37P, at 0.5 to 2.0 points of total acid, to prevent alkaline cleaner drag-in and prepare the substrate for phosphating.
To maintain the bath’s performance it should be regularly tested and adjusted to within operating parameters. Normal processing time with FREIBOND D31 is 90 seconds but processing times often range from 60 to 150 seconds. Processing parameters can vary widely based on individual processes and performance requirements. Typical operating parameters are listed below. Your Freiborne representative will help develop the proper operating parameters for your specific needs.
The pH value can be run on the negative, or free acid, side when numerous welds or laser cutting oxides are present. Consult your Freiborne representative to determine what are the optimum operating parameters for your particular situation.
The FREIBOND D31 treatment is typically followed by a rinse stage and a chrome free final seal rinse such as FREICON 33 or FREICON RSX.
Control is based on Total Acid with pH adjustment.
Total Acid Test:
Pipet a 10 ml sample into a suitable beaker or Erlenmeyer flask and add 4 drops of Indicating Solution 14 (thymolphthalein). Titrate with Testing Solution 11 (0.1N NaOH) to a permanent faint blue endpoint. Addition of 32 lbs (3 gallons) of FREIBOND D31 per 1000 gallons will raise the Total Acid by 1 point.
Pipet a 10 ml sample into a suitable beaker or Erlenmeyer flask and add 4 drops of Indicating Solution 2 (Bromcresol green). If the sample turns blue titrate with Testing Solution 20 (0.1N H2SO4) from blue to green. If the sample turns green or yellow, a negative pH adjustment value is indicated. Titrate with
Testing Solution 11 to a blue color.
Use ADDITIVE 37P to adjust the pH value down if the Total Acid is within normal operating parameters. Use FREIBOND D31 to adjust the pH value if the Total Acid is below the normal operating parameters. To lower the pH adjustment by 0.1 points, add 4 lbs (1514 mls) of FREIBOND D31 or 190 mls of ADDITIVE 37P per 1000 gallons of solution.
To raise the pH adjustment by 0.1 points, add 7 oz of NEUTRALIZER 1 per 1000 gallons of working solution.
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