Plating Types

ZINC PLATING IS ZINC PLATING - RIGHT?

ZINC PLATING IS ZINC PLATING - RIGHT?
picThere was a time in the not too distant past when practically everything was finished with generic zinc plating. Many people referred to their plating requirement as just that, zinc plate. There were rarely any requests for any particular color or specific thickness. There was never a request for so many hours of salt spray resistance. Wow have things changed.

BPS plates zinc with blue, yellow, black, olive drab, or red color. We can plate zinc in any desired thickness. These different thicknesses provide different levels of protection to the part. These many colors are not only expected to enhance the parts appearance but also to increase its ability to resist corrosion. Zinc plating is now much more than the functional coating it once was. It now has to be beautiful and actually enhance the overall appearance of the product. Our black zinc parts on a black powder coated wheelchair are a good example of this functional and cosmetic use of plating today. We have heard many times that BPS's Black Zinc and Olive Drab finishes are the best around. Ask for some samples. The finish sells itself to your customers.

Specifications!

Well anyone can attest that they are at best, slightly intimidating. If any of your zinc plating sources says Huh? to this question "What is ASTM B633-98 Type II Olive Drab Fe/Zn 25 Service Condition 4 and Bake 3 Hours at 375°F ?", then you need a new zinc plating source. This is the common, nationally recognized standard for zinc plating written by the American Society of Testing Materials. We at BPS are very familiar with all of the Zinc, Cadmium and Tin Zinc Standards including the automotive specifications. Call us and we can take some of the gobbly gook out of it and try to explain it in English.

Corrosion Resistance

We are in the rust prevention business. This is what electroplating is designed to do. There has been a dramatic increase in the amount of inquiries and question regarding salt spray testing. Salt spray testing is an accelerated corrosion test used to compare the relative protection of different metal finishes. Many question begin with "What finish do I need to last 200 hours in the standard salt spray test"? This is a whole new way of engineering parts. Our first response is usually to ask more questions about the specific requirement, like what are the failure criteria. When it comes to salt spray, the information required is how many hours until the formation of white rust (zinc oxidation) appears on the part and how many hours before red rust (iron oxidation) appears. We can give you very informed guidelines but actual testing of the specific part is the only sure way to guarantee performance. According to the ASTM Zinc specification, any colored chromate, which is referred to a Type II finish, must withstand 96 hours in the standard salt spray test without the appearance of white rust. This can be greatly improved with additional processes but this is when testing of the part in a salt spray chamber is required. We recently tested a special yellow chromate to over 250 hours before any signs of any corrosion appeared. We have tested our black zinc to over 140 hours before white rust.

Protection from the really severe environments

picSince we have been in the cadmium plating business for 35 years we are very familiar with the need for more corrosion resistance than zinc plating can provide. Cadmium provides 2-3 times the protection of zinc. It is always been the finish of choice when the part is going to be used in an aerospace or marine application, or any other critical or corrosive environment. Lately there has been some aversion to cadmium because it is a toxic heavy metal. We offer the best alternatives to cadmium. Tin Zinc and Zinc Nickel are highly resistant to corrosion because of the dual protection of the two metals. Tin Zinc and Zinc Nickel have become the finishes of choice when extremely high levels of corrosion resistance are required. We have salt spray tested our Tin Zinc and Zinc Nickel Alloys, and they resist white rust for over 200 hours and resists red rust for over 1000 hours. We are approved by the big three auto makers for our Tin-zinc process.

In the words of the singer Neil Young "Rust never sleeps". Oxidation is a destroying process that happens to anything in an oxygen environment. Yes that means humans are always oxidizing too. You may recall all the hype in health literature about anti-oxidants like beta-carotene and others. These supposedly help your body's cells from oxidizing (rusting) and possible mutating into something bad. Oxidation destroys and mutates any element over time reducing it to simpler elements. This process is called oxidation-reduction. When an iron part rusts, it is slowly turning into another compound called ferrous oxide. This red material will just fall off the part like dust until the parts original structure is eaten away bad enough to cause the part to break in service. This is why plating and other coatings are so important to the service life of all metal products. The plating will retard the eventual rusting of any metallic part. The oxidation process is busy working on the plating so the part is protected from any oxidation for an extended time. The plating business is not what it used to be. The quality of the plating finish is now considered an essential element of the total performance of a part.

Written by

Andy Scheer
Vice-President
Burbank Plating Service Corp.