Surface treatment for SB Series

Suitable for a wide range of applications, our SB Series can be used as:

  • Junction box: equipped with Ex e and/or Ex i terminals. Operating temperatures up to 150°C with our SB high temperature version.
  • Local control station: equipped with terminals, push buttons (standard and/or emergency), rotating switches, signalling lamps, measuring instruments… SB Series is also available with options such as drain valves and pass-through earth bars.
The SB series is recommended in industries where strict hygiene standards are necessary: food and beverage or pharmaceutical industries.

The right steel to prevent corrosion

Top-quality raw material plays an important role in preventing steel corrosion. For this reason, TECHNOR ITALSMEA uses AISI-316L stainless steel. Compared with lower quality stainless steel and carbon steel models, this guarantees the following advantages:

  • Higher corrosion resistance,
  • Able to withstand the most severe environmental conditions,
  • Suitable for offshore/onshore plants and in presence of oil, chemical and petrochemical substances,
  • Increased ability to withstand damages,
  • Longer lifespan,
  • Lower maintenance costs,
  • Recyclable at enclosure end of life.

Surface treatment

When high-quality raw material is not sufficient to prevent steel corrosion, surface treatments can be added. Manufacturers have studied different surface treatments to improve corrosion resistance of steel enclosures. Most common ones are:

  • ELECTRO-POLISHING: a «reverse plating» technique suitable for any metal alloy. By using a combination of chemicals and electrical current, electro-polishing carefully removes any surface imperfections and contaminants from metal parts which results in brighter and shiny surfaces. Moreover, it can be used to remove heat tint and oxide scale.
  • PASSIVATION: chemical process used to strengthen the passive protective layer and help restore contaminated stainless steel to original corrosion specifications. After an aggressive pre-cleaning operation, metal parts are placed in baskets and submersed into a diluted nitric acid or citric acid solution which removes free iron from the surface of the metal without changing the parts’ external aspect.

Electro-polishing versus passivation

Superior corrosion resistance

The electro-polishing process is often used as a more reliable alternative to passivation. The process removes the outer skin of metal and consequently embedded contaminants which can cause sub-surface corrosion. As shown in the picture, after 2,560 hours of salt spray, electro-polishing (right) guarantees a superior corrosion resistance than chemical passivation (left).

Superior hygiene qualities

When compared to passivation, the electro-polishing treatment guarantees superior hygienic qualities by preventing the growth of bacteria and germs on the enclosure surface due to an even microprofile. For this reason, chemical, pharmaceutical and food industries often require their equipment to be treated with electro-polishing to better protect the metal surface.
After electro-polishing treatment, the metal surface results ultra-smooth and fully passivated allowing a much easier and thorough cleaning.

 Electro-polished part after 144 hours of salt spray                                        Passivated part after 144 hours of salt spray

Renewed brightness of metal components

Electro-polishing treatment is also responsible for renewing stainless steel parts. The process result is bright and shiny. The passivation process is limited to the restoration of the contaminated stainless steel to original corrosion state without changing metal external aspect. 

Application to all grades of stainless steel

Since electro-polishing removes surface metal, all surface impurities are removed as well. Heavily contaminated surfaces such as machined parts, welded or brazed assemblies or other components that typically respond poorly to passivation, are good candidates for electro-polishing. Unlike passivation, 300, 400 series and precipitating grade stainless steels can be electro-polished without distortion, flash attack or hydrogen effects.

Wire weldment electro-polished               Wire weldment passivated

Application to a wide range of other metal alloys

Electro-polishing is used to enhance corrosion resistance not only on stainless steel. It offers corrosion resistance on other alloys and many companies use the process to delay the corrosion of:
  • Copper
  • Brass
  • Aluminium
  • Carbon steels
The removal of surface skin and impurities enhances the corrosion resistance properties of components. Electro-polishing may also be a solution for components which need light corrosion resistance and cannot withstand an aggressive plating operation.