Preparing surfaces before galvanizing allows eliminating marking products such as pens, industrial ink markings, indelible paint and adhesive labels. Zinc therefore cannot adhere to marked surfaces, which can cause gaps.
To avoid these gaps, it is best that the steel be bare, unpainted and unvarnished. Also, the following types of marking should be used:
- • Cold heading, whose imprint is deep enough to avoid the risk of clogging;
- • The fastening of a steel plate using a wire;
- • Weld runs
In the case of mechanically welded assemblies of elements of various thicknesses, deformations in the form of arrows or twists may occur, due to variations in the heating and cooling rate. It is then preferable to galvanize before assembly, which will subsequently be done by welding and reconditioning, or using rivets or pre-galvanized bolts.
Some deformation may also result from the galvanizing temperature, in response to the release of tension generated by welding. It is therefore preferable to plan for the welding step according to the rules established to balance the tensions.
These are usually caused by:
- • The release of existing or created tensions in the steel by welding, rolling or forming;
- • The expansion stress caused by galvanizing material assemblies who have major thickness differences at 450°C;
- • Assemblies requiring different dipping times.