Zinc plating (alkaline zinc)
Alkaline zinc bath for general corrosion protection, with trivalent passivation and friction-coefficient modifiers.
Applied with the market’s main passivations. It serves volume production parts, with protection sized to the service environment.
Low-cost sacrificial protection. It is the starting point of everything that came after.
The alkaline bath deposits zinc on iron and steel with a more uniform distribution than the acid one, especially on irregular geometry — holes, recesses and sharp corners get a layer closer to that on the flat surface. That is what makes it the bath of choice for stamped and formed parts in volume.
Protection is galvanic, by sacrifice: zinc corrodes in place of the steel. That is why thickness and passivation are not a finishing detail, they are the sizing of service life. We work with the market’s main passivations, trivalent and hexavalent, according to what the customer’s specification admits.
The bath is the same in all three colors — what changes is the passivation of the final step. White zinc, yellow zinc and black zinc come off the same deposition, and color does not change protection. ⚠️ Black zinc is not black zinc-nickel: on the part the two look alike, but one is pure zinc and the other is an alloy with 12 to 16% nickel.
Where the corrosion requirement is higher, the way is not to thicken the zinc: it is to change the alloy. Electrolytic zinc sits in the range of 200 to 300 h of salt spray, and the zinc-nickel base runs from 900 to 1,000 h — it is the conversation worth having before specifying a layer too thick for the thread tolerance.
Note: The layer and the performance are defined with our sales team according to the part and the standard of your end customer.
Technical data
- Passivation
- Trivalent
The applications that come here.
Stamped and formed parts
Production volume with irregular geometry, where the uniformity of the alkaline bath matters.
Catalog fasteners
Series lots with a corrosion requirement for indoor or sheltered atmosphere.
Component before painting
As a metallic base under an organic system, adding galvanic sacrifice to the barrier.
Variations of this line.
What specifiers usually ask.
What is the difference between alkaline zinc and acid zinc?
The distribution of the layer. The alkaline bath covers with more uniform thickness on irregular geometry — holes, recesses, corners —, while the acid one gives more brightness and deposition speed on simple parts. For a corrosion requirement with complex shape, alkaline is the way.
When is zinc not enough and zinc-nickel starts to pay off?
When the environment is marine, aggressive industrial or in permanent exposure to the weather. Electrolytic zinc sits in the range of 200 to 300 hours of salt spray; the zinc-nickel base runs from 900 to 1,000 hours at equivalent thickness. If the intended fix is to thicken the zinc, check the thread tolerance first.
Is black zinc the same thing as black zinc-nickel?
No. They are two different coatings with the same color finish. Black zinc is alkaline zinc with black trivalent passivation and sits between 200 and 300 hours of salt spray. Black zinc-nickel is an alloy with 12 to 16% nickel to ASTM B841, and the base alone runs from 900 to 1,000 hours. When the drawing says just “black”, it is worth asking which of the two.
Does trivalent passivation protect less than hexavalent?
No. Trivalent replaced hexavalent by legal requirement — in the European automotive industry, zeroed on 1 July 2007 — and, with a sealer, reaches equivalent or superior performance. The choice today is one of customer specification and regulatory restriction, not of protection.