Hot-dip galvanizing or painting ?

The advantage of hot-dip galvanizing over painting

Worldwide research shows that corrosion protection by hot-dip galvanizing (SIST EN ISO 1461 – Hot dip galvanized coatings on fabricated iron and steel articles) has a great advantage regarding the costs and the duration of protection compared to painting. The best proof are object, which surround us. The complete steel program for motorways (crash barriers, vertical signaling, bridge railings, signposts, etc.) is protected against corrosion by hot-dip galvanizing. Also, with certain exceptions, most demanding steel structures of the halls, roof structures, pipes, stable equipment, pipe, forged and balcony fences for public and individual use, walkways, chassis, caravans, agricultural equipment, new signaling railway equipment, and so on, are hot-dip galvanized.

Of course, the hot-dip galvanizing must not be confused with electroplating galvanization or metallization. The overall awareness of the cost-effectiveness of hot-dip galvanized coating is still too small in Slovenia. Nearly 7 million tons of steel is hot-dip galvanized per year in Europe. Among others, 1.4 million tons is hot-dip galvanized in Germany, 1.3 million tons in Italy, 140 thousand tons in Austria and only 20 thousand tons in Slovenia. The advantage of hot-dip galvanizing is also that it does not conceal any doubt about the quality, because the formation of zinc coating is not possible on an inadequately prepared surface, which is possible with painting. If the customer wishes or demands an additional decorative paint coating, this is simply feasible. In this case, zinc adhesive paints are used (duplex protection).

Cost and environmental benefits of hot-dip galvanizing

Starting costs of painting and starting costs of hot-dip galvanizing of 20 mm thick steel (representation of a heavier construction) are the same – approximately 15 EUR/m2 of steel surface. Within painting costs the cost of sandblasting Sa2 ½ is included, as well as the cost of the primer and two top coatings. Painting steel without cleaning the surface beforehand is not efficient, as the coating needs to be repaired after three years maximum. The thinner the steel, the more inexpensive hot-dip galvanizing is compared to painting. The price of hot dip galvanizing of 9 mm thick steel is only 9 EUR/m2, while painting costs rise to 19.5 EUR/m2. It is a known fact that hot-dip galvanized coating does not require any additional maintenance. It is sustainably protected, while high quality painted coatings need to be repaired after ten years, and subsequently even more often.

Comparison table of costs of hot-dip galvanizing and painting

PRODUCT TYPE	WALL THICKNESS (mm)	SPECIFIC SURFACE (m²/t)	GALVANIZING COSTS (EUR/t)	GALVANIZING COSTS (EUR/m²)	PAINTING COSTS (EUR/m²)
HEAVY CONSTRUCTIONS	17-25	13-15	205	16.5	14
AVERAGE CONSTRUCTIONS	13-17	15-20	230	13.5	15
LIGHT CONSTRUCTIONS	10-13	20-25	245	11	17
	8-10	25-30	280	10	18
VERY LIGHT CONSTRUCTIONS	6.6-8	30-40	325	9.5	18.5
	5-6.5	40-50	420	9	19.5
	4-5	50-65	500	8
	4	65	750	7.5
BATCH-PRODUCED ARTICLES	3	cca. 100	250	11

Source: magazin Feuerverzinken, year 2005, Publisher: Institut Feuerverzinken GmbH, Düsseldorf

Hot-dip galvanized coating is more resistant to mechanical stress

Hot dip galvanized coating is much more resistant to mechanical stress. This resistance is eight times higher than the resistance of epoxy coatings, and twenty times higher than the resistance of PVC coatings and epoxy dust coatings. The advantage of hot-dip galvanizing is that it does not allow any doubts about quality, as it is not possible to apply zinc coating to an unclean steel surface, which on the other hand is possible when applying paint.