Chromate FAQ

Below are some common questions related to trivalent and hexavalent chromates. If we did not answer you questions here or you would like to speak to a representative, please contact us and we’ll be happy to assist you.

1) What do Chromates do?

The application of Chromates to a metal part serves as a protective barrier, providing resistance to corrosion and ultimately a longer life for the part. They protect against both white and red rust on zinc-plated parts, and come in a variety of colors, including blue, yellow, black, and clear.

2) What makes Saporito’s trivalent chromate process superior?

Due to the high quality chromate used by our facility, a bright and high salt spray resistant finish can be achieved quickly and efficiently. Unlike most other chromate processes, our process does not requirstable multiple dips to achieve the same results. In addition, Saporito’s trivalent chromates are RoHs compliant and environmentally friendly.

3) What types of Chromate Solutions are available through Saporito?

Saporito strives to meet the standards laid out by the European Union and RoHS by providing both trivalent chromates in blue, yellow, and black finishes, while also meeting the needs of metal finishers working with aluminum, zinc, and cadmium by offering hexavalent chromates.

4) What is the difference between trivalent and hexavalent chromates?

Prior to the introduction of initiatives set forth by the European Union, namely the End of Life of Vehicle (ELV) and Restriction of Hazardous Substances (RoHS) initiatives, Hexavalent was the chromate of choice in a variety of industries. Since then, the use of hexavalent chromates has become limited and in many cases has been replaced by the harder, scratch-resistant Trivalent Chromate coatings, which also provide higher heat resistance. Some of the problems encountered by finishers when switching from hexavalent to trivalent chromates include color variability, ability to resist corrosion, and ease of control. Saporitos trivalent chromates address these concerns because they:

1. Produce true conversion coatings on plated alkaline non-cyanide and chloride zinc deposits
2. Offer high salt spray resistance on zinc-plated surfaces
3. are easy to control; utilizing only a single dip, our trivalent chromates are compatible with automatic feed equipment – helping to boost productivity, too.

5) How do elevated temperatures affect Chem Film?

Hexavalent chemical film conversion coating is actually a gel on a microscopic level. This gel contains water known as “waters of hydration” and this water is what imparts the “self healing” characteristics of the coating. Self healing is the process of the chem film flowing back into areas which have been scratched to protect the exposed substrate.

Over time, the waters of hydration are lost and eventually the chemical film coating loses its ability to self heal. The coating becomes chalky, powdery and can be abraded off somewhat easily at this point. On a microscopic level the coating is cracked much like dried out mud. These cracks are the in roads to the base metal where corrosive agents can find their way to attack the substrate. Chemical film coatings can however have this process sped up dramatically by exposure to elevated temperatures. As a rule, coatings should not be exposed to temperatures above 150 degrees F. The dehydration of the coating is a function of time and temperature in that it will lose the water in the coating much quicker at higher temperatures than it will at lower temperatures. A coating such as a powder coat or paint over the chemical film will trap the water keeping it from escaping easily when temperatures are elevated in the cure cycles but this only applies to the coated surfaces and any exposed areas due to selective coating will undergo dehydration.

6) How will I benefit from using Saporito’s trivalent chromates?