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Inhibition of Aluminum Corrosion in Alkaline Cleaner by the Addition of Magnesium Ions

IP.com Disclosure Number: IPCOM000052978D
Original Publication Date: 1981-Aug-01
Included in the Prior Art Database: 2005-Feb-12
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Head, NL: AUTHOR [+2]

Abstract

Aluminum substrates for computer disk products are prepared for the application of magnetic coating by first processing through a series of cleaning solutions, the first of which is an alkaline cleaner. This alkaline solution can cause pitting corrosion of the aluminum substrates, some of these pits exceeding the critical defect size and thus causing magnetic recording defects.

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Inhibition of Aluminum Corrosion in Alkaline Cleaner by the Addition of Magnesium Ions

Aluminum substrates for computer disk products are prepared for the application of magnetic coating by first processing through a series of cleaning solutions, the first of which is an alkaline cleaner. This alkaline solution can cause pitting corrosion of the aluminum substrates, some of these pits exceeding the critical defect size and thus causing magnetic recording defects.

The addition of magnesium ion prevents pitting corrosion from occurring in the alkaline solution. Specifically, at an alkaline solution concentration of 5 ounces per gallon of deionized water, and at 160 Degrees F, magnesium ion reduced pitting. Gas evolution and visual evidence of pitting both were reduced proportionately as aluminum weight loss was reduced. Pitting was undetectable when the magnesium ion concentration was 90 or more milligrams per liter of alkaline solution. At equivalent magnesium ion concentrations, magnesium nitrate and magnesium sulfate were equally effective in preventing aluminum 5086 corrosion; the anion had no effect on corrosion inhibition.

The mechanism of corrosion inhibition appears to be that of for ing a film of magnesium hydroxide/oxide on the aluminum surface. This film is removed in subsequent acidic solutions of the cleaning line and reduces the total pitting of substrates through the entire line without degrading coating adhesion. The concentration of the alkaline so...