Anticorrosive thermoplastics are more and more replacing steel, stainless steel, glass or similar materials in the chemical device and tank building industry. The main advantages of thermoplastics like Polyethylene (PE), Polypropylene (PP) and PVDF are characterised as follows:

• Extremely corrosion resistant
• Light weight
• Easy to construct (butt and bend weldable, extrusion weldable)
• Flexible
• Relatively inexpensive

The Rochling Integrated Tank Assist (RITA) programme, streamlines methods of designing, building and costing PP and PE tanks to maximise benefits of the advanced materials compared with conventional alternatives such as fibreglass.

These benefits include:

• Cost savings • Ease of fabrication • UV resistance • Impact resistance • Chemical resistance • Increased lifespan in tanks

Applications are in industries ranging from mining, mineral processing and chemical engineering to process engineering and water and waste water treatment.

One of the most important questions concerning thermoplastic engineering materials is the long-term behaviour under the influence of stress, corrosive chemicals and high temperature.

The Pure Resin is Not Enough!

To pass the temperature and corrosion tests, stabilization systems have to be added..

• PVDF is very corrosion and heat resistant without any additive.
• HDPE is robust with good chemical resistance.
• PP requires a very specific stabilization system.

These stabilizers have a brownish colour. That is why in Europe semi-finished PP products for high temperature applications (sheets, pipes and fittings) are usually dyed grey (RAL 7032 / European Grey). Compared to natural PP-types these grey extra high stabilized grades are 5 to 10 times more heat and corrosion resistant. The grey stabilized PP-types last for more than 50 years, while PP-natural will only have a lifetime of 5 to 10 years in the same applications. (NOTE: Rochling PP, stocked and supplied by Dotmar EPP, is all Stabilized.).

Conclusion:
Even at low temperatures, it’s worthwhile using stabilized high quality PP (and PE) or superior corrosion resistant materials such as PVDF for every engineering project. The slightly higher cost of these long-lasting materials compared to lower quality thermoplastics will be more than compensated for by a much longer lifetime.