Pickling Inhibiitor

The treatment of metal surfaces such as ferrous metals (iron, iron alloys and steel), copper, precious metals and aluminium alloys with strong acids for the purpose of removing inorganic contaminants, metal oxides and scale, is generally referred to as Pickling.

Pickling is one method of preparing a metal surface for processes such as electrodeposition, chemical coating, painting, etc. In a pickling process, a metal object containing, for example, a high percentage of iron, is immersed in an aqueous acid bath (usually inorganic acids), commonly called “Pickling Liquor.” On immersion, the metal oxide such as iron oxide and scale are removed by direct attack of the acid on points on the metal surface at which the iron oxide or scale attaches.

Deposits of oxide and scale are usually quite pervious to the constituents of the pickling liquor, and slough off rapidly because of the action of the acid. At the same time that the pickling liquor is attacking the metal surface directly beneath the unwanted coating, it is also attacking the already clean metal surfaces and dissolving off quantities of metal, often causing pitting or roughening, i.e., corrosion. Acid is used up needlessly in this type of chemical process. In order to prevent such corrosive attack on clean metal, inhibitors are generally added to the pickling liquor. These inhibitors slow down acid attack on clean surfaces. Thus, the rate of scale removal by pickling is substantially the same as without the inhibitor, while the loss of metal by acid corrosion is decreased.

During pickling, the acid solution reacts with the oxides to form salt of the acid. A common problem in this process is Over-Pickling which is a condition resulting when the ferrous metal remains in the pickling solution after the oxide scale is removed from the surface and the pickling solution reacts with the ferrous metal base and form hydrogen. An additional difficulty in pickling results from the liberated hydrogen being absorbed by the metal base and causing hydrogen embrittlement. Apart from this, liberated hydrogen laden with acid particles get into working premises and make it difficult to work due to its pungency. It has been customary to add pickling inhibitors to the pickling solution to overcome the aforementioned problems in pickling.

Application of Pickling Inhibitor

• Metal surface treatment
• Acidic cleaning of metal boiler tubes, heat exchangers, condensers & other related equipment’s
• Oil well acid fracturing

Advantages of Use

• Extremely effective in very small concentrations
• Increase efficiency or lifetime of metal treatment solution
• Reduce acid consumption
• Prevent hydrogen embrittlement

Konark Chemie formulates, manufacture and supply wide range of pickling inhibitors for use in various applications