Coating products with additional chromating/passivation generally results in even more corrosion-resistant properties.

Due to the introduction of EU regulation 2000/53/EG (EVL), 2002/95ER (RoHS) and 2002/96/EG (WEEE), the avoidance, and consequently, the reduction of hazardous materials is required. For corrosion-protection this means the elimination of Chrom (VI) and other hazardous materials.

Alternatives to coatings containing chromium are, for example, blue passivation or thick-film passivation which are made with Chromium III. For even more corrosion-resistance, zinc-based alloy coatings such as zinc-nickel or zinc-iron are utilised, as well as additional passivation and sealing techniques. However, please be advised that differences in color can be visibly detected when used in thick-film passivation.

This type of coating is suitable for products which require higher corrosion-resistant properties as well as parts with tensile strength ≥ 1.000 N/mm², which through the coating process is made crack stress resistant . This is due to the fact that this coating method does not induce hydrogen-embrittlement-induced cracking. However, a disadvantage is that small parts of socket head, as well as the and drilled holes are filled, and accumulation can occur as well.

Today, the most common zinc lamination techniques are:

• Dacral (produced by Dacromet, Geomet)
• Dörken (produced by Delta-Tone, Delta-Protekt)

Additional top coats provide increased corrosion protection and also adjustment to the defined thread coefficient of friction.

Lubrication additives in sealing processing can interfere with the effectiveness of the seal in chemical thread locking, especially in microencapsulated adhesives. In this case, any attempts to seal this type of coating should be rejected.

The electrical conductivity properties of the article can also be affected by the sealing process. A full evaluation may be necessary in individual cases.