Page 23

Spray January 2016

January 2016 Spray 23 Figure 2: An example of how corrosion inhibitor concentration could affect spray package service lifetime. Figure 2 provides an example from the Pair O Docs corrosion inhibitor research program. It was generated with unlined tinplated steel exposed to inhibited water at a pH of seven. The Y-axis is the spray package service lifetime estimated from electrochemical corrosion measurements and the X-axis is the inhibitor concentration. Notice that the maximum package service lifetime occurs at a 0.1% concentration. Notice also that the effective inhibitor concentration range is very narrow—spray package service life decreases when the inhibitor concentration is above and below 0.1%. There are no public domain lists of the effective corrosion inhibitor concentrations for spray formulas, so the effective concentration range in specific formulas should be determined on a case-by-case basis. Fragrance There are a small number of fragrance types that contribute to or cause spray package corrosion. However, most fragrances typically act as corrosion inhibitors. Indeed, there are numerous examples of natural ingredients that act as corrosion inhibitors with specific environments (i.e., your formula). Fragrances also have an effective concentration range for inhibiting corrosion—much like there is a fragrance concentration in your formula that gives it the optimum performance. There is no public domain date for corrosion rates as a function of fragrance concentration, so the non-corrosive concentration range for individual fragrances needs to also be determined on a case-by-case basis for specific formulas. Next month’s Corrosion Corner will feature Part 2 of the discussion on how formula ingredient concentrations affect spray package corrosion by: • Surfactants • Electrochemically active formula ingredients, copper ions, chloride ions, nitrate and sulfate ions • Propellants We would be happy to teach our Elements of Spray Package (Aerosol Container) Corrosion short course at your R&D facility. Want a specific topic discussed in an issue of Corrosion Corner? Please send your suggestion/questions/comments to rustdr@pairodocspro. com or visit www.pairodocspro.com. Back articles of Corrosion Corner are available from Spray. Thanks for your interest and I’ll see you in February. Spray


Spray January 2016
To see the actual publication please follow the link above