Oil and protective fluids for metals
Corrosion-proof metal semi-finished products 

Metalworking industries producing semi-finished metal products such as pumps, valves, flanges, heat exchangers and mechanical equipment are faced with the immense problem of the costs associated with inadequate metal component protection prior to the final application of a permanent covering (coating or paint).

The production process often consists of a sequence of steps and processes that inevitably expose surfaces to atmospheric corrosion, the result of which is the transformation of the base metal into a series of ferrous chemical compounds, ergo rust.

Environments favourable to deep atmospheric corrosion are essentially linked to three conditions:

• Non-passivated carbon steel surfaces (non-alloy)
• The presence of water
• Adequate conditions of acidity (pH below the critical threshold)

The coexistence of these conditions accelerates and promotes the transformation of the base metal into a series of reaction by-products – the iron oxides – which contribute to eroding the structure by weakening the mechanical properties. If conditions remain favourable, the action of consuming material proceeds, without pause, regenerating in a cyclic manner where only the control of one of the three variables can favour the interruption or slowing down of the process.

The use of additives in baths for mechanical turning or milling operations can help slow down such phenomena, together with protective oils and corrosion inhibitors, as the most versatile solutions in the industrial sector to reduce the risks of exposure to oxidation phenomena. Their formulation includes the following elements:

• Vehicle or base fluid (water, solvent or oil)
• Antioxidants
• Surfactants
• Fungal and bacterial growth inhibitors
• Additives for alkaline reserve

Before choosing the most suitable solution, it is necessary to understand the most critical steps in the production process and the type of materials involved. Lubricating and protective solutions are classified and chosen on the basis of certain important parameters, namely:

• Chemical nature of the vehicle – water, solvent or lubricating oil
• Type of surface film after vehicle evaporation – oily, dry or waxy
• Shelf-life – hours in salt spray as per ASTM B 117 or wet fog
• Stage of the production process where protection is required – processing, storage, testing or transport
• Type of metal to be protected
• Surface finish – machined or rough
• Safe usage – VOC-free products
• Flammability
• Biodegradability and environmental impact
• Difficulties in reaching areas to be protected – holes or areas far from the delivery point

In the metalworking industry, an effective barrier against oxidation and corrosion is an issue in many production contexts. The use of ferrous and non-alloy steels is typical for manufacturers of:

• Rotary pumps and compressors
• Hydraulic cylinders
• Oil & Gas valves
• Heat exchangers and radiators
• Woodworking machinery
• Semi-finished carbon steel products
• Flanges and Shafts

In order to guide the user in choosing the most suitable solution, we have classified temporary protectors on the basis of the following characteristics:

• Vehicle composition – water-, oil- or solvent-based
• Residual film on surface after evaporation – dry, waxy or oily
• Protective power – rated in hours of resistance in wet or salt spray