What is galvanizing?

Galvanizing is a simple process of corrosion protection consisting of dipping steel into a bath of molten zinc to produce a non-oxidising zinc-iron alloy layer on the surface. It is probably the most economic, efficient and pollution-free process available to protect steel against corrosion.

The steel which has been cleaned of grease, paint and other contaminants, is immersed in the molten zinc which has been heated to around 450 degrees centigrade.

The zinc reacts with the surface of the steel to form a progressive and highly corrosion-resistant zinc-iron alloy coating. This is metallurgical bonded layer that becomes an integral part of the steel making it extremely resistant to physical damage and rusting.

The layers can actually be harder that mild steel, which gives the total coating a very tough and durable finish.

The standard galvanize coating can have a typical maintenance free life of up to 50 years in rural areas and up to 25 year in urban/marine areas.

The process is completed under the European Standard BS EN ISO 1461.

What are the benefits?

  • Anti-corrosive
  • Durable finish
  • Maintenance free
  • Fast process – minutes
  • Up to 50 years life expectancy
  • To BS EN ISO 1461
  • Total coverage – internal and external

What is the Galvanizing process?

The Galvanizing Process we undertake at NK Coatings is described below…

Order Processing
Each item is logged on the computer tracking system on arrival so it can be traced through each stage of the galvanizing process.

The Quality team will check that material is properly prepared and vented .

Venting is vital to ensure high quality on all tubular and hollow section materials and more importantly to prevent an explosion when the steel is dipped into the hot zinc.

Important notes on venting
Inadequately vented materials can explode when immersed into the hot zinc.

Every sealed section of a tubular or hollow section fabrication MUST be vented for reasons of safety and drainage of molten zinc.

Vent holes or notches must be not more than 10 mm from the end of each sealed section and at opposite sides to provide maximum drainage.

Hole Sizes
Remember, the larger the hole, the better the drainage, the better the finish.

Section Dimension Hole Size
Up to 50 mm 2 x 12 mm
51 – 100 mm 2 x 16 mm
101 – 150 mm 2 x 20 mm
151 mm + 2 x 25 mm

The surface of the material must be free from grease, paint, weld-slag and other surface contaminants to achieve maximum surface bonding. This is achieved through our pickling or shotblasting process if necessary.

The Process

  • Acid pickle removes surface oxides and mill scale.
  • Preflux dip removes deeper oxides and prevents oxidation prior to zinc dip.
  • Zinc immersion at approximately 450°C. This forms the zinc/zinc-iron alloy coating.
  • The galvanized item is cooled in air or quenched in water.
  • The material is then hand-finished to remove excess burrs.
  • Thickness and surface condition inspections prior to delivery/collection.