VM ZINC® BASICS

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Compatibility with other material and other metals

Compatibility with other material:

Compatibility of glues and mastics with VM ZINC®

Forbidden Contacts
Direct contact with products such as fresh concrete, plaster, bitumen, mortar and structures containing substances that are aggressive towards VM ZINC®.

Chimneys
Heating oil soot resulting from imperfect combustion landing on the zinc causes irreparable damage. Regular maintenance of furnace burners and the use of fuel that meets standards prevent this damage. Using chimney "caps" may lead to aggressive deposits on the VM ZINC®. Use of an uncovered finishing cone is therefore recommended for fuel oil heating chimneys.

Contact with other metals:

Contact with metals such as copper, unprotected or ungalvanised iron or natural lead is forbidden. Only galvanised steel, natural lead protected by a patinating oil, FLEXUM® lacquered lead, aluminium and austenitic steel can come in contact with VM ZINC®.

Contact between ZINC and other metals must take into account the Electro-chemical reactions caused by a difference in electrical potential between the surfaces of the metals. Generally speaking, a metal with the highest potential on the Electro-chemical scale decomposes a metal with a lower potential and causes its destruction after a certain time by accelerating corrosion. Therefore a certain number of contacts are acceptable whilst others must be avoided.

This electro-chemical reaction:

• is accelerated in hot and humid conditions.
• is related to the electrical conductivity of the contact.
• decreases when surface treatments or natural patinas bring them closer to their standard potentials.

In the building industry, two types of contact can cause Electro-chemical corrosion: direct contact and indirect contact.

Direct Contact:

Direct contact can involve, among other things, fixing elements as well as metal decking and over flashing. In these cases of intermittent or direct surface contacts, the basic principles in the electro-chemical table should be respected. For example, the metal grounds for lightning conductors should be made of aluminium so that they are compatible with VM ZINC®. Particular attention should be paid to VM ZINC fixing elements such as clips, screws, etc.

Indirect Contact:

It is more difficult to take into account indirect contacts since they develop between metals that are at a distance from each other through a conductor (electrolyte) which is active only intermittently.

For example:
• Rainwater must never flow from a high potential metal onto a metal of lower potential. The water, in this case, becomes charged with metal ions which can destroy the weaker metal.
• The metallic reinforcement contained in concrete exposed to the weather, can set off electrolytic reactions in the presence of moisture.