Electrolytic zinc galvanizing on racks and by barrel method

Electrolytic zinc galvanizing is the most widely used electrolytic coating method of steel. This coating process ensures a reasonable protection against corrosion and a pleasant appearance of the products at low cost. Coating is also used to improve the corrosion properties and persistence of paintwork.


Alcaline electrolytic zink galvanizing on racks:

Coating thickness: 5 to 25 microns
Coated surface finish: glossy, semi glossy
Process final stage: passivation
Passivated surface finish: light blue, yellow
Maximum dimensions of the galvanized objects: 3100x1200x400


Acid electrolytic zink galvanizing on racks:

Coating thickness: 5 to 25 microns
Coated surface finish: glossy, semi glossy
Process final stage: passivation
Passivated surface finish: light blue, yellow
Maximum dimensions of the galvanized objects: 3100x1200x400


Acidic electrolytic zink galvanizing by barrel method:

Coating thickness: 6 to 12 microns
Coated surface finish: glossy
Process final stage: passivation
Passivated surface finish: light blue, yellow, green
Size of parts to be coated: max L=120 mm; diameter 8 mm; min L=15 mm; diameter 2.5 mm
Max weight of parts to be loaded into drum: 20 kg

Standards:

Electroplated coatings of zinc with supplementary treatments on iron or steel (ISO 2081:2008)
Chromatic conversion coatings based on zinc, cadmium, aluminium, zinc and zinc-aluminium alloy. Testing method (EVS-EN ISO 3613)
Hardware. Galvanic coatings (EVS-EN ISO 4042)
Corrosion tests in artificial atmospheres. Salt spray tests (ISO 9227)
Corrosion protection of metals. Galvanic coatings. Method of determining the general requirements (EVS-EN ISO 1403)
Metallic coatings on metallic substrates. Galvanic and chemical coatings. Overview of methods used to determine adhesion (EVS-EN ISO 2819)

Zinc gives base metal a cathotic protection for steel ensuring that small fringes of the coating surface will not cause direct corroding of the steel. Corrosion protection modelling is based on the time during which the coating material must withstand the development of red rust. Typically, modelling is performed by a neutral salt spray test in accordance with the ISO 9227:2006 standard.

Mostly the electrically deposited zinc coating is inactivated, to ensure that oxidation of zinc is as slow as possible. Thus passivation protects the zinc against white rust and the zinc in turn protects the base material against red rust. For ensuring protection of passivations in compliance with today’s new RoHS and ELV Directives, so-called post-dipping (sealer) is used, giving a significant improvement in corrosion performance. Resistance to white rust of the surface coatings is assessed in the final test on the basis of how long the passivation (and post-dipping) endure