Protective Coatings on Magnesium Alloys Intended for Use on Components of Airborne Vehicles
Abstract
Tin compound additions to polyvinyl butyral type clear primers provided very effective corrosion inhibition when applied to Mg-steel galvanic couples. A combination of tributyltin oxide and finely divided metallic Sn dust added to the clear primer offered the best protection by increasing the corrosion resistance 90% over non-inhibited primers. Salt spray tests showed the advantages of Sn electroplated fasteners over Cd plate when used in conjunction with Dow 17 Anodizing and various paint systems. The stannate coating was superior to Dow 17 and Cd or phosphate coated steel fastener systems. After prolonged periods of exposure at -40 degrees, electroplated Sn on steel showed a slight transformation from beta to alpha tin. After 650 hr exposure, the corrosion characteristics of Mg alloy painted and unpainted panels (with and without steel fasteners comparing Dow 17 anodizing and the stannate coating) were very encouraging. The conductivity of the stannate coating was 8.0 microhms/sq in. as compared to 7.0 microhms for bare Mg and a high of 74,000 microhms for Dow 17 thin anodize.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 05, 1961
- Accession Number
- AD0267826