FORMCOAT 5 is an immersion zinc phosphate coating process for use in the cold forming industry when used in conjunction with a FORMLUBE lubricant, or wire drawing when used in conjunction with a FORMATE series drawing compound. FORMCOAT 5 contains special additives to produce a uniform coating and reduce chemical losses due to drag-out.
• The process tank should be constructed from stainless steel or an acid and oxidizer resistant
composite material that will withstand the temperature ranges required. Use of mild steel will result in shortened equipment life due to chemical attack.
• Heat transfer surfaces should be constructed of 316 stainless steel, or an acid and oxidizer
resistant high temperature composite, if steam or heat transfer fluid type heat exchangers are used.
• Piping and pumps may be constructed of stainless steel, mild steel, or an appropriate composite material. Use of mild steel will result in shortened equipment life.
Fill the tank to the three quarter level with water and add 77.5 gallons (1000 LBS) of FORMCOAT 5A chemical for each 1,000 gallons of working solution required. With water bring the tank to the operational level and heat to the required temperature range of 170°CF to 200°CF, typically 180°CF. Once the optimum temperature is determined, it should be maintained within ±5°CF. Just before any work is processed, add 10 oz.(220 mL) of FREIDOX 2 or 20 oz.(500ml) of a 20% solution of FREIDOX 1 per 1,000 gallons and mix. A processing bath built up according to these recommendations will result in 23 points of Total Acid, or what is referred to as a 25 point bath. Cleaned steel is placed in this solution for 3 to 10 minutes to produce a uniform coating.
To calculate the amount of FORMCOAT 5A necessary to build up a bath use the following equation:
(Working Volume) x (Total Acid Points Desired) x (0.00338) = Volume of FORMCOAT 5A Required
Example: To build up a 5000 gallon working volume bath at 30 points of total acid
(5000 gal) x (30 points) x (0.003247) = 507 gallons of FORMCOAT 5A required
Just before any work is processed, add 10 oz. (220 mls.) of Freidox 2 or 20 oz. (500 mls. of a 20% solution of Freidox 1) per 1,000 gallons and mix.
The treatment process for FORMCOAT 5 is generally as follows:
1. Cleaning with a FREICLEAN series cleaner
2. Hot water rinse
4. Cold water spray rinse
5. Cold water rinse
6. Hot water preheat
7. FORMCOAT 5
8. Cold water rinse
9. Hot NEUTRALIZER rinse
10. FORMLUBE soap or polymer series lubricant
To maintain the bath’s performance it should be regularly tested and adjusted to within operating parameters. Normal processing time with FORMCOAT 5 is 3 to 10 minutes. 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.
Insoluble phosphate sludge will be generated as a natural byproduct of the FORMCOAT 5 reaction with the steel. This sludge must be periodically removed to prevent it from depositing on the surface of the steel being coated, as it is abrasive in nature and therefore very detrimental to forming operation.
Maintaining the temperature of the rinse prior to FORMCOAT 5 as close to the temperature of the FORMCOAT 5 as possible will reduce both chemical consumption and sludge generation.
If the FORMCOAT 5 phosphating solution is continually heated when not in used excess free acid will be generated resulting in a low TA/FA ratio. To avoid this situation the tank temperature should be lowered during long periods of inactivity.
Testing and control of a FORMCOAT 5 bath is based on Total Acid and Total Acid/Free Acid ratio (TA/FARatio) according to the following table.
Total Acid: Using a 5ml volumetric pipette, transfer a 5ml sample of the FORMCOAT 5 into a clean 250ml Erlenmeyer flask (adding up to 50ml of DI water to the flask may aid in viewing the endpoint). Add 5 drops of Indicating Solution #3 (Phenolphthalein) and titrate with Testing Solution #11 (0.1 N NaOH) to a slight pink endpoint. Record the buret reading as the Total Acid.
Free Acid: Using a 5ml volumetric pipette, transfer a 5ml sample of the FORMCOAT 5 into a clean 250ml Erlenmeyer flask (adding up to 50ml of DI water to the flask may aid in viewing the endpoint). Add 5-10 drops of Indicating Solution #11 (Bromophenol Blue) and titrate with Testing Solution #11 (0.1 N NaOH) to a blue-green endpoint (absence of yellow). Record the buret reading as the Free Acid.
TA/FA Ratio: Divide the total acid reading by the free acid reading to obtain the TA/FA ratio
TA/FA Ratio: For a fresh bath this is normally in the 6.0-9.0 range. If this ratio drops below 6.0, discontinue using FORMCOAT 5B replenishing chemical and use FORMCOAT 5A until the ratio is above 6.0. If, even with proper testing and control, your TA/FA ratio is routinely out contact your Freiborne
representative about using a modified replenisher.
An addition of 28 lbs. (2.1 gallons) of FORMCOAT 5B per 1000 gallons of solution will raise the Total Acid 1.0 point.
An addition of 43 lbs. (3.4 gallons) of FORMCOAT 5A per 1000 gallons of solution will raise the Total Acid by 1.0 point.
FREIDOX TESTING: (recommended after bath is idle for more than 4 hours or if the bath exhibits an abnormal color)
Dip a strip of Indicator Paper 17 into the working solution. If it turns pink FREIDOX must be added, as above, until a fresh piece of paper does not change color. If it should turn pink the bath is on the “iron side” and further work should not be processed until sufficient “Freidox” is added to kick out the iron from the solution. This can be done using the same quantities, in increments, as with a new bath.
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