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Chromate Technology
Luster-On Products took its name from the breakthrough chromate technology that our predecessor company developed back in the late 40’s. The ability of our chromate to leave a luster on electroplated zinc
and cadmium deposits led us to the forefront of chromate technology. As we open to a new century, Luster-On again has been challenged by chromate requirements. Today, finishers, manufacturers, engineers
and end-users are looking for a hexavalent free chromate that can offer desired corrosion protection without overshadowing safety, health and environmental concerns.
The New Look of Protection
Luster-On answers the challenge with Tridescent, a hexavalent-free, trivalent chromate, providing over 125 hours of 5% neutral salt spray protection. The chromate is a unique blend of trivalent chromium
complexes, accelerators and activators that contains no hexavalent chromium compounds nor compounds that will produce the hexavalent ion in situ or within the film. The chromate is steady state in nature
providing a uniform, consistent finish from day to day, week to week.
The Chromate Conversion Coating
The film generated by Tridescent is generally greenish in color with varied shades of iridescence ranging from pink to yellow to blue. It contains, on average, 10-15mg of chromium per square foot with
film thickness in range of 20-30 microinches. Longer immersion times and higher operating temperatures can increase film thickness. The film readily accepts traditional chromate dyes but yields light or
pastel colors due to its light background. Testing has also shown that the film has some of the self-healing characteristics so typical of the colored hexavalent films.
Chromate and Then Bake
The Tridescent chromate conversion coating has the added feature of withstanding temperatures of 400° F during a standard eight-hour treatment for hydrogen embrittlement without significant loss of corrosion protection. The Tridescent, which fits into the existing chromate cycle, therefore can be applied immediately after plating reducing costs of a second chromate step after baking.
An Automotive Answer
The Tridescent fits into all automakers’ plans to eliminate the presence of hexavalent chromium while maintaining the integrity of the chromate film. Tridescent successfully yields a chromate conversion
coating on all traditional zinc deposits as well as the zinc-cobalt, zinc-nickel and zinc-iron alloys offering excellent corrosion protection. Presently, the Tridescent is in use in production meeting
the European automakers standards already in effect.
Operation and Maintenance
Similar to most chromates, control of concentration, pH, temperature and immersion time yields a consistent chromate film. Each of the four key factors has its own effect on the film and corrosion
protection. Each variable is controlled easily with readily available laboratory equipment lending to its ease of operation. Dissolution of iron and zinc may affect slowly the integrity of the solution
so it is important to keep the solution free from fallen parts or lost barrel loads. If metallic contamination is limited, the lifetime of the chromate solution will be lengthy.
Our goal is to continue to meet the challenges offered by chromate users and to keep the luster on all of our customers electrodeposited zinc and zinc alloys. Tridescent is the next product in line of a
proud history of chromates.
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