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Zinc and Zinc Alloy Passivates and Sealants

Example of how passivated zinc and zinc alloy deposits improve corrosion protection against rust

Technical Corrosion Protection

Corrosion protection is one of the fundamental tasks in electroplating technology. Zinc- and zinc alloy processes from Schloetter offer a high-quality and cost-effective protection for functional components which are inseparably linked with our post-treatments.

By now, the well-engineered chromium (VI)-free passivating processes are established in a leading market position. Processes based on Cr(VI) are still requested for certain applications. Schloetter provides the entire range of passivation and chromating completed by a variety of Sealants.

Summary of Chromium (VI)-free Passivation Processes for Zinc

Bath No. Process Name Type of Electrolyte Description
09002 Passivation
SLOTOPAS PA 1030
Zinc
(THIN LAYER)
blue
cobalt-free process with excellent corrosion protection and appealing appearance
09133 Passivation
SLOTOPAS Z 30 T
Zinc
(THIN LAYER)
blue
produces on all electroplated zinc Surfaces an intensive bluish temperable protection layer
09045 Thin Layer Passivation
SLOTOPAS Z 20 Blue
Zinc
(THIN LAYER)
blue
cost-effective corrosion protection with an attractive appearance
09043-1 Thick Layer Passivation
SLOTOPAS HK 10 (cold)
Zinc
iridescent
A low temperature version of SLOTOPAS HK10 with improved corrosion protection compared to Z20 Blue
09043 Thick Layer Passivation
SLOTOPAS HK 10
Zinc
(THICK LAYER)
iridescent
highest corrosion protection on zinc coatings
09102 Yellow Passivation
SLOTOPAS G 20
Zinc
(THICK LAYER)
yellow
yellow passivation with all characteristics of a usual thick layer passivation
09106 Black Passivation
SLOTOPAS Z 60
Zinc
(THICK LAYER)
black
black corrosion protection layers with an excellent appearance on zinc coatings deposited from alkaline processes

Examples of zinc plated deposits

Summary of Chromium (VI)-free Passivation Processes for Zinc Alloys

Bath No. Process Name Type of Electrolyte Description
09058 Passivation
SLOTOPAS ZNT 80
Zinc-Nickel
(THIN LAYER)
transparent
process with high corrosion protection and transparent, stainless steel-like appearance
09115 Passivation
SLOTOPAS ZNC 50
Zinc-Nickel
(THIN LAYER)
iridescent
produces a coloured iridescent chromium(VI)- and cobalt-free passivation layer with good corrosion behaviour
09116 Thin Layer Passivation
SLOTOPAS ZNB 60
Zinc-Nickel
(THIN LAYER)
blue
produces uniform blue, cobalt- and fluoride-free passivation layers e.g.
for the marking of special parts
09130 Thick Layer Passivation
SLOTOPAS ZN 300
Zinc-Nickel
(THICK LAYER)
black
produces black, weakly iridescent cobalt-free protection layers with excellent appearance


In Salt Spray Tests in accordance with DIN EN ISO 9227 our passivation does not show any reduction of corrosion protection even after heat treatment at 120 °C / 24 hours.

Chromium (VI)-free Post-Treatments
Thin Layer Passivation for Zinc

09045 Thin Layer Passivation SLOTOPAS Z 20 Blue

Thin Layer Passivation SLOTOPAS Z 20 Blue contains Cr(III), fluoride and an iron inhibitor. It produces an intensive blue-violet protection layer on zinc deposits, providing excellent corrosion resistance. If the system is operated correctly the results of corrosion protection in accordance with DIN EN ISO 9217 is > 24 hour without white rust even without sealing.

The required corrosion resistance of the protection layers is also excellent after tempering (at 120 °C / 24 hours). The colour of the finish does not degrade significantly during hydrogen de-embrittlement at 200 °C - 210 °C, but the corrosion resistance decreases.

However, tests have proven that 2 - 3 hours of heat treatment at 150 °C does not affect the corrosion resistance.

For special applications e.g. the plating of steel tubes (hollow), Inhibitor SLOTOPAS ZB is added to inhibit the dissolution of iron even further and also increases the working life of the solution.

09133 Passivation SLOTOPAS Z 30 T

The Passivation SLOTOPAS Z 30 T is a thin layer passivation and contains chromium(III) compounds, fluorides and is free of Cr(IV). An iron inhibitor can be added separately. Passivation SLOTOPAS Z 30 T produces on all electroplated zinc coatings an intensive bluish chromium (VI)-free passivation layer with an extraordinary well corrosion protection. Passivation SLOTOPAS Z 30 T is mainly intended for the passivation of barrel parts.

The required corrosion resistance according to DIN 50979 is significantly exceeded. The corrosion resistance of the protection layer is also ensured during tempering (24 h, 120 °C). If tempering with higher temperatures (200 - 210 °C), like applied for hydrogen de-embrittlement, the discolouration is very low.

A temperature load of 8 hours up to 210 °C does not affect the corrosion resistance.

09043-1 Passivation SLOTOPAS HK 10 (Cold)

SLOTOPAS HK 10 is a passivating process for electroplated zinc coatings and is chrome (VI) -free. Thick Layer Passivation SLOTOPAS HK 10 produces a slightly blue-yellow-green iridescent finish on zinc deposits. The corrosion resistance is excellent and is equivalent to the protecting effects of a yellow-chromating process based on chrome (VI).

more examples of zinc and zinc alloy passivated coatings

Chromium (VI)- and Cobalt-free Post-Treatments
Thin Layer Passivation for Zinc; cobalt-free

09002 Passivation SLOTOPAS PA 1030

The Passivation SLOTOPAS PA 1030 is a process for passivating of zinc electroplated surfaces, whereby it’s regardless if the zinc coatings are deposited from cyanide, acid or alkaline zinc electrolytes. The passivation is a one-step process for passivating both rack- and barrel parts.

The Passivation SLOTOPAS PA 1030 contains chromium (III) compounds and fluoride but is free from cobalt. The Passivation SLOTOPAS PA 1030 produces a blue-violet uniform protection layer and has a wide range of tolerance regarding concentration and immersion time and can be easily monitored and corrected.

If Passivation SLOTOPAS PA 1030 is operated correctly, the passivation has a long service life. The required corrosion resistance according to DIN 50979 can easily be achieved and often considerably exceeded.

Chromium (VI)-free Post-Treatments
Thin Layer Passivation for Zinc-Nickel

09058 Thin Layer Passivation SLOTOPAS ZNT 80

SLOTOPAS ZNT 80 is a transparent passivating process for electroplated zinc-nickel alloy coatings. The Passivation SLOTOPAS ZNT 80 produces a uniform transparent Cr(VI)-free protection layer on zinc-nickel alloys with good corrosion protection.

The Passivation SLOTOPAS ZNT 80 contains trivalent chrome compounds and fluoride. The electrolyte is operated with only one liquid additive.

Laboratory tests certify an excellent corrosion resistance in accordance with DIN EN ISO 9227 (with and without previous heat aging 24 hours / 120 °C) so the required corrosion values  as specified by DIN 50979 will be significantly exceeded.

09116 Passivation SLOTOPAS ZNB 60

Passivation SLOTOPAS ZNB 60 produces on zinc-nickel coatings a blue protection layer with good corrosion behaviour. This colouration is especially useful if plated parts should be marked.

The Passivation SLOTOPAS ZNB 60 contains chromium (III) compounds and is free from Cr(VI), cobalt and fluoride.

The requirements of DIN 50979 on corrosion resistance of the layer systems are met with and without previous heat ageing (24 h / 120 °C) for rack as well as for barrel parts.

Examples of zinc alloy plated pasrts and passivated for ant-corrosion protection

Chromium (VI)-free Post-Treatments
Thick Layer Passivation for Zinc and Zinc-Iron

09043 Thick Layer Passivation SLOTOPAS HK 10

SLOTOPAS HK 10 is a passivating process for electro deposited zinc and zinc-iron coatings. The conversion layers applied by dipping show on zinc surfaces a slightly bluish-yellowish-greenish appearance while on zinc-iron alloy coatings intensive yellowish-greenish conversion layers are formed. The achievable corrosion resistance is excellent and comparable to the protecting effects of a yellow chromating electrolyte based on Cr(VI). Analyses on series parts confirm a minimum requirement of 72 hours for barrel parts and 168 hours for rack parts relating to surface corrosion (white rust) in the Salt Spray Tests in accordance with DIN EN ISO 9227.

Additional sealing with a product of our SLOTOFIN series gives a uniform transparent surface finish and increases the corrosion protection again.

Chromium (VI)-free Post-Treatments
Yellow passivation for Zinc

09102 Yellow passivation SLOTOPAS G 20

SLOTOPAS G 20 is a Cr(VI)-free passivating process for electroplated zinc coatings. Yellow Passivation SLOTOPAS G 20 is an immersion process and produces yellow-reddish/green protective layers on zinc coatings. The corrosion resistance is excellent and is equivalent to the protecting effects of a yellow-chromating electrolyte based on Cr(VI).

Tempering of the protection layer up to temperatures of > 80 °C does not affect the corrosion protection quality, compared to yellow chromated Cr(VI) zinc surfaces.

Chromium (VI)-free Post-Treatments
Thick Layer Passivation for Zinc-Nickel

09115 Passivation SLOTOPAS ZNC 50

The Passivation SLOTOPAS ZNC 50 is for the passivation of electrodeposited zinc-nickel alloy layers. On zinc-nickel surfaces, it produces a colourful iridescent, chromium (VI)-free passivation layer with a good corrosion behaviour.

The Passivation SLOTOPAS ZNC 50 contains trivalent chrome compounds and is free from Cr (VI) and cobalt.

Requirements on the corrosion resistance of the layer system as specified by DIN 50979 are fulfilled with and without previous heat ageing (24 h at 120 °C) for both rack and barrel parts.

Zinc passivated coatings

Chromium (VI)-free Post-Treatments
Black Passivation for Zn and Zn-Ni

09106 Black Passivation SLOTOPAS Z 60

SLOTOPAS Z 60 is a passivating process based on trivalent chromium that produces black conversion layers on alkaline zinc coatings with good corrosion protection. The corrosion protection is excellent and at least equal to the protecting effects of chromium(VI)-based chromating processes. Heat treatment of the protection layer up to temperatures of 120 °C tends towards an improvement of the protection characters.

We strongly recommend a post-treatment with a sealing of our SLOTOFIN series if Black Passivation SLOTOPAS Z 60 is used. This has two positive effects:

  • the achievable corrosion protection will be increased
  • it gives a uniform and brighter appearance

09130 Passivation SLOTOPAS ZN 300

The Passivation SLOTOPAS ZN 300 contains trivalent chromium-compounds and fluoride but is free of cobalt and Cr(VI).

On zinc-nickel coatings black and weakly iridescent passivation layers are generated. Passivation SLOTOPAS ZN 300 is applied in combination with a subsequent post-dip solution, organic sealant or topcoats.

Passivation SLOTOPAS ZN 300 in combination with Post-Dip Solution NT 10 or a corresponding sealant from our SLOTOFIN series gives a uniform black surface with excellent corrosion resistance.

Summary of Chromium (VI) based passivates

Bath No. Process Name Additives Applied On
09150 Chromating
METAPAS F yellow CA
liquid zinc
09151 Chromating
METAPAS F black CA
liquid zinc
09156 Chromating
METAPAS F olive CA
liquid acid zinc

Yellow Chromating for Zinc

09150 Chromating METAPAS F yellow CA

The Chromating METAPAS F yellow CA is a process for yellow chromating of electroplated zinc coatings. The Chromating METAPAS F yellow CA forms yellow iridescent zinc coatings and is suitable for coatings deposited from acidic as well as alkaline and cyanide electrolytes. The metal removal rate is low. Rack- and barrel parts can be chrome plated in the same good way. In difficult cases, the good adhesion of the chromate film can still be improved by the use of Post-Dip Solution CC, while at the same time the corrosion resistance is increased. The chromating is made-up and operated with liquid concentrates.

Black Chromating for Zinc

09151 Chromating METAPAS F black CA

The Chromating METAPAS F black CA is a process for black chromating of electro deposited zinc coatings.

Make-up is performed with one liquid concentrate. A liquid product is also used for the pH adjustment.

The black chromating is applied at room temperature and forms deep black, uniform surfaces which are abrasion- and flex-resistant in dry condition. Chromating METAPAS F black CA can be used for both rack and barrel application.

Olive Chromating for Zinc

09156 Chromating METAPAS olive CA

The Chromating METAPAS olive CA is preferably used for chromating of zinc coatings which were deposited from acidic electrolytes. Chromating METAPAS olive CA forms dark olive to green chromate films and can be used for both rack- and barrel applications. It’s supplied as liquid concentrate.

Black chromated deposits

Summary of Sealants and Other Post-Treatments

Bath No. Process Name Particular Characteristics
09033 Sealant
SLOTOFIN 10
all-purpose organic sealant
09064 Sealant
SLOTOFIN 40
mixed sealant, contains nanoscale particles
09068 Sealant
SLOTOFIN 80
inorganic sealant for a complicated part geometry; excellent optic
09057 Post-Dip Solution
SLOTOPAS NT 10
post-passivation with similar characteristics as a sealant

Sealants

09033 Sealant SLOTOFIN 10

Sealant SLOTOFIN 10 is used for post-treatment of chromated or passivated zinc and zinc alloy surfaces. If the solution is operated with Sealant Concentrate SLOTOFIN 11 only, a clear transparent, organic protecting layer is achieved after drying, which increases the corrosion protection and improves the resistance towards fingerprints as well as the appearance of the coating. Sealing of blue chromated or passivated zinc layers and transparent chromated or passivated zinc alloy coatings with SLOTOFIN 10 results in an uniform transparent appearance of the parts. The iridescence of yellow chromated or passivated surfaces disappears and yields to a weak yellowish uniform colour.

The intensity of the colour and the optic of black chromated respectively passivated surfaces can be increased by adding Dye Concentrate SLOTOFIN 13. Besides that, colour irregularities that may have occurred due to the black chromating or passivating process can be compensated. We recommend sealing mass-produced bulk articles are sealed outside of the plating plant. The same is recommended for rack parts that are treated in Sealant SLOTOFIN 10 which is pigmented black with Dye Concentrate SLOTOFIN 13. The SLOTOFIN protecting layer can be applied wet-to-wet as well as on pre-dried parts.

09064 Sealant SLOTOFIN 40

The Sealant SLOTOFIN 40 is used for post-treatment of chromated or passivated zinc and zinc alloy surfaces. It is based on an organic polymer and contains nanoscaled silicon compounds. Sealant SLOTOFIN 40 is operated with two additives, Sealing Concentrate SLOTOFIN 41 and Sealing Concentrate SLOTOFIN 42. It gives a clear, transparent and inorganic-organic protective surface film after drying, which not only increases the corrosion protection and optical appearance, but also decreases the sensitiveness towards fingerprints. It is recommended that mass-produced bulk articles are sealed outside of the plating line. Hot-soak degreasers are used to remove the SLOTOFIN coatings from jigs or centrifuge baskets.

more zinc passivated components

Sealants and Other Post-Treatments

09068 Sealant SLOTOFIN 80

The Sealant SLOTOFIN 80 is an aqueous-alkaline, chromium (VI)-free solution which contains non-organic polysilicates. It is used for post-treatment of passivated zinc and zinc alloy surfaces.

Research shows, that the corrosion protection on zinc plated and passivated parts can be increased to > 400 hours in the neutral salt spray test as specified by DIN ISO EN 9227.

The Sealant SLOTOFIN 80 is free of volatile organic compounds.

09057 Post-Dip Solution SLOTOPAS NT 10

The Post-Dip Solution SLOTOPAS NT 10 is applied on already passivated zinc-nickel coatings.

Post-Dip Solution SLOTOPAS NT 10 is an alternative to usually applied Sealants on black passivated layers and makes them less sensitive to touching, abrasion and scratches and ensures the required corrosion protection.

Transparent passivated zinc-nickel coatings treated with Post-Dip Solution SLOTOPAS NT 10 become almost insensitive to fingerprints. This simplifies the handling of the parts enormously. SLOTOPAS NT 10 is a completely inorganic post-treatment which can be applied if organic based Sealants are forbidden e.g. for pipes.

parts showing selant and post-dip applications

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Schloetter Co Ltd

Abbey Works
New Road
Pershore
Worcs, UK
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