FORMCOAT 28 is designed to deposit a tight-grained, dense, high quality zinc phosphate coating on steel surfaces with smaller crystal sizes than typical cold forming phosphates (generally 30-100 μm crystal size on standard 1010 steel panels). FORMCOAT 28 is used primarily to facilitate cold forming when used in conjunction with a FORMLUBE lubricant, or wire drawing when used in conjunction with a FORMATE series drawing compound. FORMCOAT 28 is particularly suited for use under our Polymer series of lubricants due to the refined crystal structure and the lower film weights associated with Polymer lubricants.
Formulated to deposit a dark tight-grained, dense, high quality zinc phosphate coating on steel surfaces with smaller crystal sizes than typical cold forming phosphates. FORMCOAT 28 is used primarily to facilitate cold forming when used in conjunction with a FORMLUBE lubricant, or wire drawing when used in conjunction with a FORMATE series drawing compound. FORMCOAT 28 is particularly suited for use under our Polymer series of lubricants due to the refined crystal structure and the lower film weights associated with Polymer lubricants.
• 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 73 gallons (970 LBS) of FORMCOAT 28A 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, typically 180oF. Once the optimum temperature is determined, it should be maintained within ±5oF. A processing bath built up according to these recommendations will result in 24 points of Total Acid, or what is referred to as a 24 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 28A necessary to build up a bath use the following equation: (Working Volume) x (Total Acid Points Desired) x (0.00304) = Volume of FORMCOAT 28A Required
Example: To build up a 5000 gallon working volume bath at 25 points of total acid
(5000 gallons) x (25 points) x (0.00304) = 380 gallons of FORMCOAT 28A 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 28 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 28
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 28 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 epresentative will help develop the proper operating parameters for your specific needs.
Insoluble phosphate sludge will be generated as a natural byproduct of the FORMCOAT 28 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. The frequency of sludge removal will depend on the processing parameters and the type and surface area of steel being processed.
Maintaining the temperature of the rinse prior to FORMCOAT 28 as close to the temperature of the FORMCOAT 28 as possible will reduce both chemical consumption and sludge generation.
If the FORMCOAT 28 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, preferably to 160oF or lower.
Testing and control of a FORMCOAT 28 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 28 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 28 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 #11 (Bromophenol Blue) and titrate with Testing Solution #11 (0.1 N NaOH) to a blue-green endpoint. 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 5.5-7.5 range. If this ratio drops below 5.8, discontinue using FORMCOAT 28B replenishing chemical and use FORMCOAT 28A until the ratio is above 6.0. If, even with proper testing and control, your TA/FA ratio is routinely out of the recommended control
parameters contact your Freiborne representative about using a modified replenisher.
TA/FA Ratio 5.8-7.5
An addition of 0.23% v/v FORMCOAT 28B will raise the Total Acid 1.0 point. (Target TA – Actual TA) x Tank Volume x 0.0023 = Amount of FORMCOAT 28B to add (25.0 – 22.4) x 5000 gallons x 0.0022 = 28.6 gallons Replenisher (FORMCOAT 28B)
TA/FA Ratio <5.8
An addition of 0.3% v/v FORMCOAT 28A will raise the Total Acid by 1.0 point. (Target TA – Actual TA) x Tank Volume x 0.003 = Amount of FORMCOAT 28A to add (25.0 – 22.4) x 5000 gallons x 0.003 = 39 gallons Makeup (FORMCOAT 28A)
FREIDOX TESTING: (recommended after bath is idle for more than 4 hours.)
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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