Wetting Agent Wash: Adhesion Problems On Zinc And Galvanized Surfaces

2023 Author: Hannah Pearcy | [email protected]. Last modified: 2023-11-26 11:39

Large areas of paint flaking can often be observed on galvanized substrates. What needs to be taken into account to prevent such damage?

Zinc and galvanized surfaces

Zinc sheet or galvanized steel are used as components (doors, railings, facing) on the building. Pre-treatment at the factory, such as chemical passivation, phosphating or oiling, cannot be reliably recognized using methods customary on construction sites. Even the smallest amounts of oily or greasy contaminants can lead to adhesion problems in the subsequent coating. Careful preparation of the zinc surface for the adhesive strength of a subsequent coating is therefore essential.

The ammonical wetting agent wash

Ammoniacal wetting agent washing has proven itself. This is a cleaning liquid made up of 10 liters of water and 0.5 liters of 25 percent ammonia spirit plus a splash of non-greasing household cleaner. Detergents based on soaps are generally unsuitable. The cleaning liquid is applied to the zinc surface. Wash with a plastic fleece in abrasive movements, then rinse thoroughly with plenty of clean water. Drying, especially in joints and crevices, must be ensured before coating. Commercial cleaning agents for zinc surfaces are to be used according to the manufacturer's instructions. The choice of coating materials is based on the subsequent stress. Coating materials for zinc surfaces are specially formulated and their suitability for zinc surfaces must be guaranteed by the manufacturer, as with the "ProZink Plus" thick-film coating from ZERO. Modified alkyd resin products and 2-component epoxy resin primers (solvent or water dilutable) are suitable for the first coating on zinc surfaces. Two-component PUR primers and lacquers (solvent or water-dilutable) should also be used. Normal alkyd resin primers and paints are unsuitable. A chemical reaction between zinc and alkyd resin leads to loss of adhesion and embrittlement; large-scale flaking is the painfully visible result. Modified alkyd resin products and 2-component epoxy resin primers (solvent or water dilutable) are suitable for the first coating on zinc surfaces. Two-component PUR primers and lacquers (solvent or water-dilutable) should also be used. Normal alkyd resin primers and paints are unsuitable. A chemical reaction between zinc and alkyd resin leads to loss of adhesion and embrittlement; large-scale flaking is the painfully visible result. Modified alkyd resin products and 2-component epoxy resin primers (solvent or water dilutable) are suitable for the first coating on zinc surfaces. Two-component PUR primers and lacquers (solvent or water-dilutable) should also be used. Normal alkyd resin primers and paints are unsuitable. A chemical reaction between zinc and alkyd resin leads to loss of adhesion and embrittlement; large-scale flaking is the painfully visible result.large-scale flaking is the painfully visible result.large-scale flaking is the painfully visible result. Tip The BFS Leaflet No. 5 describes the points relevant for the coating of zinc and galvanized steel and refers to DIN standards. [email protected]