Hi everyone, to properly address the issue of oxidization on magnesium there are several great articles on the internet. Some of the best articles are on aircraft maintenance websites. What I have done is take the motor apart to address the issue of corrosion thoroughly inside and outside the cases. I clean the cases with gunk brand engine degreaser, a new unused plastic brush, and or a new unused plastic scaper since our mag cases are rather soft. This process avoids introducing any dissimilar metals or contaminants that may get entrapped in the mag cases and be the cause of future corrosion or cause adhesion issues for paint or epoxy later on. I soak the cases in a 5 gal bucket of very hot water and redo the process until the cases are very clean. I then empty and clean well this same bucket or a new one and pour in a mixture of 1 gallon Zip Chem products Calla 855 heavy duty Alkaline cleaner with 3 gallons of boiling hot water and let soak for an hour. I rinse the cases and dry the cases with dry compressed air or paper towels. I tape off all the bearing surfaces then blast the inside and outside of the cases in a blasting cabinet with crushed walnuts. I use a max of 110 psig. You will end up with beautiful dull silver magnesium. Remove tape. Use dry compressed air to clean the cases and put in the oven at 200 F for an hour to get rid of all moisture.
I know this probably sounds like overkill but what you're doing is sweating out the oil that the cases have soaked. I spray Prekote Surface Pretreatment or Dow 19 Chromatic Conversion to minimize future corrosion. The Prekote spray you can buy in a quart spray bottle which should be plenty and it's less toxic then the Dow 19 stuff for sure. You can use high temp epoxy such as JB Weld twin tubes that include a red tube and black tube, dries gray, for smaller pits inside the motor. For the bigger pits I like filling them with the tig mg filler rod material AZ92. If you have pits, cracks or other type of damage inside or outside your cases you can now tig weld by using argon and mag filler rod AZ92. Then clean the cases with some more calla 855 by wiping some on where I have done repairs and then rinse with water. I then respray with Prekote or Dow 19 Chromatic conversion. I then paint the inside and outside of the cases with none etching epoxy primer then your final color of choice over the none etching epoxy anticorrosion primer. NEVER use etching primer or paints on magnesium since they creat corrosion.
You can buy all these items from Skygeek.com website.
You really need to treat the cases like they are a magnesium part of an aircraft to get lasting results. As an alternative you can find shops that do aircraft maintenance and they will do all these things for a very reasonable charge including tig welding, surface treatment and painting. Even small local executive airports have repair shops or know of one. Be sure to read and follow all the instructions of the products you buy.
I know this probably sounds like overkill but what you're doing is sweating out the oil that the cases have soaked. I spray Prekote Surface Pretreatment or Dow 19 Chromatic Conversion to minimize future corrosion. The Prekote spray you can buy in a quart spray bottle which should be plenty and it's less toxic then the Dow 19 stuff for sure. You can use high temp epoxy such as JB Weld twin tubes that include a red tube and black tube, dries gray, for smaller pits inside the motor. For the bigger pits I like filling them with the tig mg filler rod material AZ92. If you have pits, cracks or other type of damage inside or outside your cases you can now tig weld by using argon and mag filler rod AZ92. Then clean the cases with some more calla 855 by wiping some on where I have done repairs and then rinse with water. I then respray with Prekote or Dow 19 Chromatic conversion. I then paint the inside and outside of the cases with none etching epoxy primer then your final color of choice over the none etching epoxy anticorrosion primer. NEVER use etching primer or paints on magnesium since they creat corrosion.
You can buy all these items from Skygeek.com website.
You really need to treat the cases like they are a magnesium part of an aircraft to get lasting results. As an alternative you can find shops that do aircraft maintenance and they will do all these things for a very reasonable charge including tig welding, surface treatment and painting. Even small local executive airports have repair shops or know of one. Be sure to read and follow all the instructions of the products you buy.