Registered in England No. 1725990 Q & A / Advice - Corrosion Prevention: Corrosion is a recognised problem throughout the printing industry. If it is not prevented or controlled it can have a considerable degenerative effect on presses, resulting in expensive component replacement and reduced press life. Newspaper presses suffer from especially high levels of corrosion, due mainly to the aggressive nature of the newsprint used and the combination of contact- free or spray damping systems and bi-directional web operation, causing both sided of cylinders and rollers to be continually saturated. Sheetfed presses are also prone to corrosion, although here the damage is generally aggravated by self-adhesive packings, which trap a build up of moisture on cylinders, and by the regular use, all too often, of unsuitable solvents on machine surfaces; typically these are low priced and highly aromatic products, such as strong petroleum distillates. The causes of corrosion: Corrosion is cause by the aggressive nature of certain press chemicals and by the effects of electolytic action resulting from contract between metal surfaces and, generally, liquids such as fountain solutions, cleaning agents, solvents and water. For corrosion to occur on printing presses, these liquids must contain high levels of ionogenic chlorides, which can make process solutions highly acidic. Tap water can contain levels of ionogenic compounds as high as 2--ppm; the level at which corrosion can start is 25ppm. Although Ionogenic compounds are a necessary part of the formulation of many process solutions, they generally represent only 0.05% of the total concentrate, making solutions in their undiluted state almost neutral, being in the region of 5.0 on the pH scale. This level is insufficient to cause corrosion. When combined with water, especially water containing high concentrations of naturally occuring chlorides, the pH levels can, however, be altered dramatically towards the lower  end of the scale, creating aggressive and highly corrosive substances. It should be realised that the level of acidity, depends not on the quantity of concentrate added but on the quality of water used. In particular, soft or de-mineralised water can adversely affect the pH value of the solution so it is vital to understand the composition of the water supply when formulating fountain solution additives, if corrosion is to be avaoided. MAN-Roland, Koenig & Bauer (KBA), Wifag and Goss approve the use of Vegra anti-corrosion products as part of a regular maintenance schedule. The Solution: One possible solution, driven by the need both to overcome problems of corrosion and comply with the changing legislation, is to use vegetable based materials, especially for cleaning. Although these have low rates of evaporation, their cleaning properties are limited and, perhaps more importantly, they will cause blankets and rubber rollers to swell and shrink after only a brief period of use. If addition, there are a number of problems associated with their storage and disposal, while citrus based products have a question mark hanging over the harmful effect they can have on human skin. The alternative is to use solutions based on aliphatic or paraffinic hydrocarbons, such as Vegra Rapid Wash, rather than aromatic compounds. These provide an effective cleaning medium, which does not affect the properties of rubber, and give the added benefits of a high flash point, ease of disposal and limited evaporation. They are also considerably less harmful to skin and give off only very low odour. Extensive research carried out by Vegra GmbH on behalf of press manufacturers, has shown that the use of special additives in process chemicals, especially fountain solutions, will inhibit corrosion, without affecting their overall performance. The additives used function by using special buffer compounds, to compensate for the increased chloride levels introduced by the addition of water, effectively holding pH levels within a narrow band. These compounds also help to clean non-image areas on plates and prevent oxidation, while limiting the build-up of ink and paper on the blankets, thereby reducing the transfer of a potentially harmful cocktail of materials to press components that are sensitive to corrosion. The points to remember: In essence, effective and long-term prevention of corrosion can be achieved by: o the use of corrosion inhibited press chemicals, especially fountain solutions and blanket and roller washes. o the elimination of press chemicals of unknown or acidic formulation. o the use of specifically designed oils and greases for lubricating cylinders and bearings. Pomeroy have a range of specially formulated corrosion inhibiting process chemicals, including Vegra fountain solutions and blanket and roller washes, to protect your press(es) against the long-term effects of corrosion. The possible influence of materials on corrosion in printing presses: -  Press Chemicals  -  Chloride in tap water  - Inks  - Paper  -  Blankets  -        Press Chemicals. Fountain    Chemicals for      Cleaning Solutions. plate treatment. Solvents.   © Pomeroy Pressroom Products Ltd 2010 Website design by: AH Designs Cylinder Conserver Fount Solutions Vegra Rapid Washes Acidic components. Strong acids. Acid gum. Abrasive materials. Dangerous Aromatic solvents (plastic polymer treated surfaces) Chlorinated hydrocarbons.