Zinc Plating

The primary purpose of Zinc Plating is to protect the Base Material   (normally Steel) from Corrosion (Rust).

So... what do you need to know?

Well, Zinc does a relatively good job of protecting Steel.

As an example, many Automotive Brake Calipers are electroplated with Zinc. Brake Calipers experience a difficult environment of summer / winter / salt / snow / heat / cold / etc...

However, the Brake Calipers will eventually Rust / Corrode and will need to be replaced (how long this takes is an unknown question and depends upon Climate and Conditions).

Will the Brake Calipers exceed the useful life of the car? Can we use a cheaper and more "Cost Effective" Corrosion Resistant Coating??? Can we use a different and cheaper material versus the Zinc Plated Steel??? These are all difficult questions...

 

Anyway, Electroplated Zinc is very commonly used to protect Steel, and sometimes used to add "Decorative Effect" and increase Corrosion Protection for Zinc Die Castings (Zamak).

A few times we have seen Zinc Plating used within the Electronics Industry over Copper Base Material, but these applications are relatively rare...

 

Cosmetics and Colors...

It needs to be completely understood that in most cases, Zinc is a purely Functional Coating.

By "Functional Coating"... we mean that the primary pupose of the Zinc Coating is to provide Corrosion Protection. However, in certain cases it can be very "Decorative" (and look very similar to Decorative Chrome) and is often used for such purposes in addition to the Corrosion Protection...

By using Chemical Processing Solutions (after the Zinc Electroplating Process) called Passivates, we are able to add extra Corrosion Protection AND "Color" the Zinc Plated Parts / Components.

 



The Possible Colors are...

1) Black

2) Yellow

3) "Decorative Chrome Appearance / Bright Zinc Plating" - here a Plating Shop with Acid Zinc can come very close to making Your Parts / Components look like True Decorative Chrome. Acid Zinc has some "Leveling Effect" to help "cover up" / "smooth out" some Surface Imperfections of the Base Material.

4) Matte – this cosmetic choice has been popular recently within the Window Fittings Industry. It is a general matte grey surface and can be somewhat compared to a "Satin Nickel" Finish.

5) "Clear / Transparent / Colorless" - by using Specific Passivates we can create a "Clear / Transparent / Colorless" Passivate Layer that simply shows the Natural Color of Zinc ("Metallic Silver"). This type of Passivate would be classified as a "Thin Film Passivate".

6) "Blue" - again, by using Specific Passivates we can create a Slight "Metallic Blue" Color. This would also be classified as a "Thin Film Passivate".

7) "Slightly Iridescent" - and again, by using specific Passivates we can obtain anything between "Colorless to Slightly Blue to Slightly Iridescent". Any of these "Colors" would be classified as "Thin Film Passivates".

8) "Iridescent" - by using a Thick Film Passivate... we will normally obtain a Part / Component with significant amounts of Iridescence.

In the "Old Days" we used to get drunk...    :  )

In the "Old Days" (and actually still today)... we used Chromates instead of Passivates. Chromates contain Cr (VI) / Hexavalent Chromium... and Passivates contain Cr (III) / Trivalent Chromium.

Due to the Carcinogenic Properties of Cr (VI)... the European Union "outlawed" / banned the use of Chromates. This forced many OEMs to change their Specifications and therefore the use of Chromates has decreased dramatically.

Anyway... Chromates ARE still in use... and ISO 2081:2008 gives the following guidance for... 

 

Chromate Conversion Coating Type and Appearance and a Coating Surface Density...

 

HOWEVER... the reason we DO NOT LIKE THIS STANDARD is...

 

As you can see in the "NOTE" Section... ISO 2081:2008 states, "All Chromate Coatings MIGHT or might not contain Hexavalent Chromium Ions." 

 

We therefore recommend that if the Zinc Coating Requirements are for a Cr (VI) Free Passivation Coating... that you stay away from ISO 2081:2008 and use DIN 50979 to create your Zinc Specifications!!! 

 

Our opinion is the ISO 2081:2008 is NOT a RoHS Complaint Standard and therefore can not be used to Produce or Sell Zinc Plated Products in / into the European Union.

 



Again, back to the "Good Old Days"...



So... if your Zinc Plated Parts / Components REQUIRE the use of a Chromate (Hexavalent Chromium Containing)... we would therefore recommend that you use ISO 2081:2008.

The above Table does an adequate job of describing the various "Cosmetics / Colors" that you can expect... etc...

 

More and More Information... 

As an OEM (Part / Component Designer), a Tier 1 or 2 Supplier, or an Electroplating Engineer... you essentially have two choices for the Zinc Electroplating Process...

Acid Zinc or...

Alkaline Zinc.

There are VERY important differences between these two types of Electroplating Solutions... so we therefore STRONGLY recommend that you thoroughly read our discussions on Acid Zinc and Alkaline Zinc

Also, if you are seriously considering Zinc Plating... we recommend that you read our discussion concerning the Disadvantages of Zinc Plating.

We also have a discussion concerning Zinc Plating Lines and this discussion will give you a better understanding of the overall process.

 

 

Zinc Plating Specifications...



We will soon have a full discussion concerning "Zinc Plating Specifications". If you need help in creating a Specification for your Parts / Components... please Contact Us... and we will do our best to help you and your company.

 

Generally, the Specification is relatively simple… however… it is “what is behind the Specification” where the difficulty lies…

Anyway… let us keep to the “general idea”…    :  )

When creating a Specification you would normally “Document” the Zinc Plating Specification on the Part / Component Drawing… we give the following example…

DIN 50979 – Fe//Zn8//Cn//T2

In simple terms… the above Zinc Plating Specification refers to an Iron or Steel Base Material… followed by a Minimum Zinc Coating Thickness of 8 microns (315 microinches)… followed by a Thick Film Passivate… followed by a Sealant.

So… FIRST you state the STANDARD (examples… normally DIN 50979, ISO 2081:2008, or ASTM B663-11). Many Automotive OEMs will have their own Standards (example Volkswagon’s TL 244).

SECOND you identify the Base Material – which for the above Standards must always be Fe… referring to Iron or Steel.

THIRD you identify the “Electroplated Coating”… which is Zn for Zinc Plating, ZnFe for Zinc Iron Plating, and ZnNi for Zinc Nickel Plating. This is immediately followed by the Minimum Thickness Requirement (in the above Specification we have determined a Minimum Thickness of 8 microns / 315 microinches).

FOURTH you identify the Chromate or Passivate Coating!!! Here is where we run into some differences between STANDARDS… and therefore you will have to refer to the specific STANDARD to identify the “Abbreviation / Code” for the Chromate or Passivate. In our above listed DIN STANDARD… the “Cn” refers to an Iridescent Thick Film Passivate.

FIFTH you identify whether a Sealant is required or not… In our above example… T2 refers to the Application of a Sealant. T0 would indicate that NO SEALANT is required.

At this point in time we will not get into a discussion concerning “Heat Treatments” either before the Electroplating Process (normally to Harden Steel)… nor will be get into the discussion concerning “Baking” to relieve and reduce the risk of Hydrogen Embrittlement.

 

New Developments...

Recently (let us say in the last five to ten years), there has been a significant increase in the demand for Zinc Nickel Plating by the Automotive Industry.

The Automotive Industry likes the Zinc Nickel Deposit / Coating because it performs much better than the Zinc Deposit / Coating in the "Real World Field Environment".

As we have stated above, if you do not find the information you are looking for... please send us your Questions.

 

 

Further Technical Information...

Click here for technical information concerning Zinc Anodes and information on Anode Bags.

Click here for information concerning Amp-Hours and Zinc Plating Solutions.

Click here for information concerning Air Agitation for Zinc Plating...

For Barrel Plating, the Selection and Sizing of the Barrel Danglers is extremely important!!! 

Click here for information on Plating Current Density.

 

And click here for a discussion on Cathode and Anode Bars...

 

 

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Here you will find valuable information on the Zinc Plating Process... if you don't find the information you are looking for please click here to send us your Questions...

 

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plating bolts

 

BELOW... As an example... many Brake Calipers are plated with Zinc...

zink plated brake calipers

 

Pictured Below: It is possible to "Color" Your Parts / Components Black...

And... Yellow...