Spray galvanising is a variant of flame spraying according to DIN EN 657/DIN EN ISO 14919 / DVS 2302 for all elements not suitable for hot galvanising Chromed or nitrated elements are unsuitable, amongst others. During spray galvanising a 1/8" zinc wire is melted by a flame in wire flame spraying or arc spraying and finely pulverised on the work piece with pressed air.
The particles in spray galvanising build a micro porous coating on the work piece that has been pre-treated by sand blasting SA3 according to DIN 55928 part 4 which have equally good corrosion protection features as coating achieved by hot galvanising. The surface becomes very absorbent through spray galvanising and can be additionally sealed as described below.
Recommended minimum strengths according to DIN EN 22063:1993 / DVS 2302 are 50 µm to 200 µm in spray galvanising, and can be made stronger at the client's request. The agents for spray galvanising are specified according to DIN EN ISO 14919 Tab.4.
Spray galvanising generates smoke and dust and therefore the work should be carried out by qualified, certified staff to guarantee environmental and employment protection in compliance with DVS2314.
The corrosion level in spray galvanising coating is good in alkaline media at pH7 – pH12 and can be applied in dry atmospheres up to 250°C. For values of pH4-pH9 and temperatures up to 600°C aluminium, spray aluminium galvanising and aluminium spraying should be avoided. The agent ZnAl15 can also be added in spray galvanising, which then works against chlorine up to ca. 300°C and with improved properties and in particular in a SO2-containing atmosphere.
A coating by spray galvanising is a high quality base coat. If a long corrosion protection with constant water penetration or atmospherical exposure is required through spray galvanising the surface - also called duplex systems - can also be coated with PVC, Acrylate, Epoxy and Polyurethane resin. The additional coat should be applied immediately after the cooling of the element, to avoid an oxidised and salty residue on the zinc surface.
The advantage of spray galvanising (ca. 60°C) also in comparison with hot galvanising (at ca.450°C) is that the thermal exposure of the work piece can be disregarded and deformations can be excluded in large surfaces too. The disadvantage is that hollow spaces or difficult accessible places (recipients, undercuts, inner pipes etc.) cannot be treated with spray galvanising.