Zinc Phosphate Conversion Coating - Freiborne Industries, Inc Zinc Phosphate Conversion Coating - Freiborne Industries, Inc

Product Type: Freibond 4

FREIBOND 4 chemicals are conversion coating agents designed to impart a high quality zinc phosphate coating to steel and galvanized surfaces. Freibond 4 is particularly effective in preventing whit spots, seediness, and pin-point buildup. Small amounts of aluminum can also be treated successfully in mixed metal production.


FREIBOND 4 chemicals are conversion coating agents designed to impart a high quality zinc phosphate coating to steel and galvanized surfaces. Small amounts of aluminum can also be treated successfully in mixed metal production.

FREIBOND 4A Make-up Chemical
FREIBOND 4B Replenishing Chemical
FREIDOX 2 Accelerator Chemical
FREICLEAN Metal Cleaning Chemical
FREICON Non-chrome final seal rinse

Stainless steel, mild steel, and high temperature acid resistant plastics are suitable for processing equipment. Utilizing 300 series stainless steel equipment will significantly increase the service life of the equipment. Full cone spray nozzles, such as Spraying Systems WhirlJet® nozzles, are normally used in spray applications to ensure uniform application of FREIBOND 4. Spray pressures should be maintained at 15 psig for optimum coating. Spray pressure above
20 psig will create inconsistencies and voids in the iron phosphate coating.

Utilization of deionized or reverse osmosis water in the system will reduce both chemical consumption and sludge generation. Application equipment should be cleaned or a regular maintenance cycle with PICKLE 2 to remove sludge and scale deposits that may interfere with application and subsequent performance.

The typical process sequence for FREIBOND 4application consists of the following steps:

1. FREICLEAN treatment
2. Hot water Rinse
3. Water Rinse
5. Cold Water rinse
6. Cold Water Rinse
7. FREICON post treatment seal
8. Drying

The tank is charged to the 3/4 level with water and for each 100 gallons of working solution
required add 53 lbs. (18 liters or 5 gals.) of FREIBOND 4A. Top up with water, mix and bring temperature to the operating range of 150°CF- 170°CF.

When steel is being treated additions of FREIDOX 2 must be made as follows:

Add 5 oz. (108 ml or 1/4 pint) of FREIDOX 2 per 100 gallons OR 10 oz. (250 ml or 1/2 pint) of a 20% solution of FREIDOX 1 per 100 gallons and mix thoroughly. Continuous addition of FREIDOX2 is recommended for spray applications where steel is being processed.

Separate replenishing chemicals are employed depending on whether FREIDOX 2 is used or not. When FREIDOX 2 is used, use FREIBOND 4B and when it is not in use, use FREIBOND 4C.

Spray operation normally requires 1 minute at 150°C – 160°CF; immersion 1-3 minutes at 150°C -170°CF.

Total Acid Test:
Pipet a 10 ml sample into a suitable beaker or Erlenmeyer flask and add 5-10 drops of Indicating Solution 3 (phenolphthalein). Titrate with Testing Solution 11 (0.1N NaOH) to a permanent pink endpoint.

A FREIBOND 4 solution made up as above will give a 26 point reading. Maintain the Total Acid in the range of 25 – 27 points. An addition of 1.6 lbs. (0.5 liter or 1.1 pints) per 100 gallons of FREIBOND 4B or FREIBOND 4C will raise the Total Acid by 1 point. Replace any drop in points due to mechanical loss (leaks, spills, etc) with FREIBOND 4A by adding 2.0 lbs. (0.7 liter or 1/2 pint) for each point required.

FREIDOX 2: (This is only required where steel is being processed)

Dip a strip of Indicator Paper 17 into the working solution. If it turns pink FREIDOX 2 must be added, as above, until a fresh piece of paper does not change color.

When no change in color occurs, determine the FREIDOX 2 concentration as follows: Pipet a 25 ml sample into a 250 ml beaker, add 10 – 20 drops of Testing Solution 44 (50% H2SO4) and titrate with Testing Solution 15 (0.042N KMnO4), swirling vigorously until a persistent (10 second) pink is obtained. Maintain the FREIDOX 2 concentration between 0.5 and 2.5 points.

An addition of 2 oz. (43 ml or 0.1 pint) of FREIDOX 2 will increase the concentration by about 1 point.


Additional Information

Temp Range



Carbon Steel, Galvanized Steel, Aluminum


Paint Pretreatment, Rubber-Metal Bonding

Product Type

Conversion Coatings

Product Line



Spray or Immersion

Ordering Information

To place an order, please contact our knowledgeable and professional customer service team:

If you are unable to find what you need or require a custom formula, please call and speak with one of our knowledgeable Formula Engineers. They can walk you through the ordering process quickly and professionally.