Internal treatment

Unless otherwise specified, it is implied that all internal surfaces will be accurately washed through the circulation of hot mineral oil for transformers in accordance with ISO 4406, filtered with a 120um net filter so as to leave as little impurity as possible in circulation.
Convett radiators design with its oval shape tube has an important competitive advantage against the stamped plate radiators even in the internal cleanness. In fact the oval shape of the tube is much smother and much easier to clean then the stamped plate elements which are made by two coils welded together with all the impurity that can be stocked between them.
If explicitly requested in the order, a degreasing treatment with solvents will be carried out together with internal painting with isolating resins resistant to hot oil, with a thickness of approximately 10 microns.
If explicitly required we can also paint the flanges in the area where you attach the valve, as shown in the picture below.

External treatment

Depending on the external environment where the transformer is located and the warranty period required. Upon request we can provide you the suggested painting cycle for any specific environment.
In general find below the useful table based on

  • Standard ISO 9223:1992. Corrosion of metals and alloys — Corrosivity of atmospheres – Classification. It categorizes environments on the basis of wet time, as well as sulphur dioxide and chloride contents.
  • Standard ISO 9224 Corrosion of metals and alloys — Corrosivity of atmospheres — Guiding values for the corrosivity categories gives the corrosion rates of steel, zinc, copper and aluminium in the first five years.
  • Standard EN ISO 12944-2 Paints and varnishes — Corrosion protection of steel structures by protective paint systems — Part 2: Classification of environments
  • Standard ISO 14713 protection against corrosion of iron and steel in structures — Zinc and aluminium coatings – Guidelines

which gives examples of the environments in each corrosion category and the rates of corrosion for steel and zinc in the first year

Before any type of painting we treat 100% of the surface with a metallic sandblasting with white metal, in accordance with specifications SSPC-SP5-63 laid down by the Steel Structures Painting Council, with a maximum profile thickness of 60 microns.
The appearance of the sandblasted surface must correspond to grade Sa3 contemplated by Svensk Standard SIS 055900-67.
After max. thirty minutes the most delicate parts of the radiator are protected by a primer.
If explicitly requested in the order, hot-dip-galvanized radiators will be supplied, in accordance with CEI 7-6 standards and UNI-EN ISO 1461. The mechanical construction of our radiators prevents them from warping during hot-dip galvanization.
In accordance with the environmental conditions, and the warranty required in cooperation with our paint supplier we can provide you with the recommended product and cycle. Below find please some typical examples*:

  • Regions like Saudi Arabia or Qatar require 220-240 um NDFT with acrylic or polyurethane top coat
  • Siberia require 170-180 um NDFT with acrylic or polyurethane top coat (-40C to 80C resistant)
  • Northern climates require hot dip galvanized steel with 100-140 um NDFT coating system
  • Particularly heavy industrial sites require 160-240 um NDFT epoxyurethane or acrylurethane coating systems
(Data from