Alkaline Zinc

There are three options for Zinc Plating...

1) Alkaline Zinc

2) Acid Zinc

3) And Cyanide Zinc

Because of the dangers and tough regulations of working with Cyanide... there are not so many plating companies using Cyanide Zinc compared to Alkaline and Acid Zincs.

alkaline zink

Advantages of Alkaline...

There are a lot of advantages for the Alkaline System... the biggest advantage by far is...

Excellent Thickness Distribution...

A typical Thickness Distribution for the Alkaline System is about 8 um (315 micro inches) in the LCD (Low Current Density) Areas, and 16 um (630 micro inches) in the HCD (High Current Density) Areas.

Compare this to a Typical Thickness Distribution for Acid Zinc... about 4 um (157 micro inches) in the LCD areas, and 40 um (1570 micro inches) in the HCD!!!

Another Big Advantage!!!

Another big advantage of the Alkaline System is that Load Sizes (how many Parts / Components or more specifically how much Surface Area) for Rack Plating can be about three times greater versus Acid Zinc. Therefore... a typical Load Size for 1000 L of Acid Zinc can be around 200 dm2 and a typical load size for 1000 L of Alkaline Zinc can be around 600 dm2.

The above facts can lead us to a general statement... that in most cases... "Throughput" (amount of Parts / Components produced per hour, per day, etc...) will be greater in Rack Plating with Alkaline Zinc.

Other Advantages...

There are many other advantages with Alkaline Zinc Plating including the fact that the solution is less corrosive to the Zinc Plating Line and Plating Equipment compared to Acid Zinc...

Also... Yellow and Black Passivates and Chromates look better with Alkaline Zinc versus Acid Zinc...

Disadvantages!!!

The biggest disadvantage of Alkaline Zinc is that it is not as "Bright and Beautiful" as Acid Zinc. We can compare the pictures below...

Picture of the "Ugly / Stainy" Alkaline Zinc...

Compared to the "Bright and Beautiful Decorative Chrome" Appearance of Acid Zinc...

So... whereas Acid Zinc can be used (kind of) as a "Decorative Finish"... Alkaline Zinc should NEVER be expected to be a Bright "Decorative Finish" and we must always remember that the Primary Purpose of Zinc Plating is as a "Functional Corrosion Protection Coating"!!!

Maybe (and we state MAYBE)... Yellow and Black Zinc Plating with Alkaline Zinc... can have a somewhat "Decorative" Effect, and these "Colors" can also be used for "Identification Purposes".

More Disadvantages... Speed and Carbonate!!!

The next Disadvantage we list is the Alkaline Zinc Process Speed (the time it takes to reach a Specified Plating Thickness). As we have stated elsewhere within Our Website... Acid Zinc is much faster than Alkaline Zinc. With Acid Zinc it can take about 10 minutes to reach 8 microns / 315 micro inches in HCD (High Current Density) Areas. With Alkaline Zinc it will take 20 minutes.

For Sodium based Alkaline Zinc Plating Solutions... Carbonate will build up in the solution over time... and this will cause the Alkaline Zinc Plating Solution to become "Less Efficient" and therefore Plating Speed will continue to become slower and slower. It is possible to purchase Equipment that will "freeze-out" (precipitate out) the Carbonate and therefore keep the "Efficiency" Higher and the Plating Speeds Faster.

A typical efficiency for a Sodium Based Alkaline Zinc is 50%. 

It is also possible to use Potassium based Alkaline Zinc Plating Solutions... in which the Carbonate does not have such an effect upon Efficiency and Plating Speed.

A typical efficiency for a Potassium Based Alkaline Zinc is 75%.

CAST IRON

Lastly, Alkaline Zinc is unable to effectively plate Cast Iron Parts / Components.

For Cast Iron Parts / Components... we MUST use Acid Zinc.




Exit Alkaline Zinc and Return to Zinc Plating...

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Above... another picture of a part plated with Alkaline Zinc. For "Clear Zinc Plating" Applications...

Alkaline Zinc will have more Iridescence versus Acid Zinc.

Also, in general, Plating Stains might be more noticeable... and Alkaline Zinc will never be as Bright as Acid Zinc.

 

HOWEVER!!! With the Application of a Specific Sealant... all Iridescence and Stain Issues will be completely "Covered" and your Parts / Components will have a very Uniform Appearance... see Picture below... 



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