The treated metal surface will typically have a gray to blue iridescent or blue-gold iridescent color, depending on the coating weight and the base metal.
A typical iron phosphate consists of: •phosphate acid base • accelerators/oxidizers •surfactant package (optional)
The first question you might ask is “Why Phosphate?” There are three major reasons why phosphating can be beneficial to your operation:
1. Form a stable inert coating on the metal surface.
2. Provide excellent paint adhesion.
3. Inhibit the spread of corrosion from a damaged area.
Phosphate chemicals are mildly acidic solutions containing accelerators and surfactants. They can be applied over a wide temperature and pH range. The coating weight of phosphate can vary from 15 milligrams per square foot to 100 milligrams per square foot depending on the process used.
Iron Phosphate : pre-treatment powder coating
In an iron phosphate solution, the metal surface is etched, releasing some iron into the bath. When metal ions are etched from the part surface, the surface becomes positively charged. The metal ions in the bath are converted to iron phosphate, negatively charged.
A pH rise occurs at the interface of the solution and the part, causing the ions to deposit an amorphous coating on the metal surface.
The acid salt content, type and amount of accelerator, and the type and amount of acid etchants varies from one compound to another. These compositions are all moderately acidic. Although crystal site activators are not typically required prior to application of iron phosphate coatings, formulations commonly contain oxidizers and/or accelerators.
The oxidizers, such as nitrite or chlorate, act to initiate attack on ferrous parts, providing the iron for the iron phosphate coating. Accelerators, such as molybdate or vanadate, provide active sites for iron phosphate deposition.
Choice of oxidizer or accelerator in a particular product may affect the performance or appearance of the final coating.
In a three-stage treatment process, the cleaning and coating are combined by incorporation of a detergent surfactant package in the iron phosphate solution. A source of fluoride ions may be added if aluminum is also being processed to increase the etching effect on the oxide surface of the aluminum.
Iron Phosphate Application Options
The coatings can be applied by hand wiping, with a handheld spray wand, immersion, or a spray washer. The number and type of process stages is directly dependent on finished part requirements.
A cleaner/coater combination followed by a rinse is the typical minimum chemical cleaning and phosphating process used. The addition of stages in the process can provide enhanced performance.
At Kyler Mech Powder Coating , we also offer this as an alternative to Zinc Phosphate pre-treatment prior to powder coating.
Depending on your requirements , Kyler Mech Powder Coating can assist you to determine the best and most cost effective processes required to deliver the best result for you.
Whether its high quality finishes for durable outdoor use, or less durability required for indoor applications , we will provide you with the highest quality powder coated products at a respectable turn around.
So , Iron Phosphate or Zinc – the choice is yours.