Caustics based products are used where the soil is difficult to remove (carbonised or polymerised) or where we need a large chemical energy because the physical energy input and or the time is low. Caustic foam or gel products are used on heavy soiling such as ovens.
Low foam or foam suppressed caustic products are used in most CIP systems, in tray or crate washers and for boiling or soak cleaning of cookers or fryers. The addition of a hydrogen peroxide to caustic solutions creates oxygen release and turbulence in the solution thus aiding soil removal. This process needs careful control to avoid ‘boiling over’ of hot caustic solutions.
Caustic products clean by hydrolysing organic soils as well as saponifying fatty materials. Caustic products will not always effectively remove heavy protein films, such as those that build up in abattoirs or on meat slicers. For these applications, a chlorinated product is preferred.
Caustic products will always cause water hardness to precipitate as a scale. To prevent this, products in this category contain scale control agents. It is important to always identify the hardness of the water used to dilute the product and then match the final product concentration to the water hardness.
As a rule, the scale control agents in caustic products will not dissolve mineral scales, for this an acidic product is required. However, the scale control agents will interact with calcium and magnesium compounds in soils to aid breakup, but for this to be effective it is essential to use a product above the minimum concentration required for water hardness control.
Sodium hydroxide (NaOH), caustic, is manufactured by the electrolysis of brine solutions. Originally this was performed using a mercury electrode, the result was that sodium hydroxide always contained trace levels of mercury. Modern production processes are mercury free and typically produce sodium hydroxide as a solution of 50% wt./wt. concentration.
50% wt./wt. solutions of sodium hydroxide have SG values of 1.52 @ 20ºC, meaning that solutions are very heavy. Furthermore, the freezing point of a 50% wt./wt. solution of NaOH is very high, making it difficult to use and deliver in the winter, unless tanks and pipes are trace heated and lagged.