Traditionally, iron or zinc phosphating (in various versions) was chosen for the pre-treatment process, which provided the required quality and performance.
Recently, solutions have emerged to replace this traditional technology with products that address the growing concerns about energy and water consumption, environmental impact, and overall process support.
Iron phosphate systems, also known as alkali metal phosphates, are used for parts that require a durable finish but are not exposed to highly corrosive environments. These systems may have two to six stages, the shortest sequence being the process line cleaning step followed by rinsing with tap water and / or demi. Short sequence systems are used if the quality requirements are low.
Parts that are more difficult to clean or have higher quality requirements require a separate cleaning stage, appropriate flushing tanks, iron phosphate, final rinsing and demi rinsing. Rinsing after treatment (with or without chromium) improves the corrosive effect of phosphate itself.
Iron phosphate processes are much easier to handle and require fewer steps than zinc phosphating. However, iron phosphates do not provide the corrosion protection provided by zinc phosphates.
The zinc phosphate system differs from the iron system in two critical areas. First, it requires the use of a surface conditioner stage. Secondly, the zinc phosphate bath has additional metal ions in solution, which are incorporated into the coating along with the metal ions from the substrate being processed.
Zinc phosphate coatings provide exceptional durability of the painted part in corrosive environments and have the ability to coat mixed metals (steel, galvanized steel and aluminum). Over the past few years, several minor changes have been made, such as reducing environmental impact, improving performance and ease of use. New zinc phosphate systems operate at lower temperatures, in some cases are free from nitrite and nickel and offer sludge reduction.
New products allow you to increase quality and ease of use.
New generation conversion coatings
There are currently new conversion coating technologies on the market that have four significant advantages.
These processes are shorter, simpler and operate at lower temperatures than current zinc or iron phosphate processes. They work well on all standard steel, zinc and aluminum substrates. Significantly reduce the environmental impact, and their corrosion resistance meets the metal finish specifications for painted metal substrates. All these benefits provide significant cost savings for manufacturers who want to upgrade their installations.
The new generation conversion coating process is based on zirconium and additional chemical properties. When applied to a metal substrate, these chemicals react to form an amorphous 20-80 nm thick zirconia coating that is significantly different from the currently used iron phosphate and zinc phosphate coatings. The new coating is thinner than traditional iron or zinc phosphate conversion coatings.