Dissimilar metal corrosion

Two questions, I have a 20 year old purchased 6A, the left side step was damaged and unusable when I purchased it, yesterday when I removed the step for replacement with a new step, I found dissimilar metal corrosion between the aluminum and the steel, the aluminum had not been correctly treated in that area prior to assembly.
Question one, what is the correct way to remove the corrosion, it does not appear very deep, then what is the procedure to treat the aluminum and steel of the new step as it goes back together, I would like to use rattle cans as I don’t have any product setting around.
Question two, is acceptable to attach the step with machine screws as I do not have any riveting equipment, however I can borrow some, old step was attached with about ten or twelve rivets, how many screws should be used, the rivet holes in the aluminum will be covered up by the new step and would not be a problem.

I appreciate your expertise Thanks for your input.
2022 paid, exempt, but one of the best investments I make every year.
RV6A
RV6 regrettably sold.

I'll leave it to someone smarter than me to answer the first question about corrosion, but as far as the fasteners, the Van's step kit gives builder the option of solid rivets or pull rivets. I opted for pull rivets.
I don't have the step kit plans handy, but Van's support could probably tell you which pull rivets to use.

I used screws with nyloc nut. Works fine. PM if you want a picture. When I put them on there was lots of crack problems so I figured screws were a good idea. Since I had them reinforced so probably not as big of a deal now.

John Tierney said:

I'll leave it to someone smarter than me to answer the first question about corrosion, but as far as the fasteners, the Van's step kit gives builder the option of solid rivets or pull rivets. I opted for pull rivets.
I don't have the step kit plans handy, but Van's support could probably tell you which pull rivets to use.

Click to expand...

Two ways to discourage corrosion, (1) sealing and (2)sealing w/active ingredients.

For (2), There are rattle can primers with zinc chromate, although out of stock. Consider the topcoat as some spray can primers will curdle under certain topcoats. A little home work here.

The aluminum side can be cleaned mechanically, followed by metal prep from Aircraft Spruce, followed by distiller water rinse and finally alodine treatment of the raw aluminum. Alodine (or equal) is a chromate surface conversion and increases paint adherence too. With a chromate primer, the zinc will become the sacrificial element keeping corrosion from creeping under the primer and top coat.

You can spray/topcoat and wet install the screws/rivets to add to the anti- corrosion protection while you are at it. Not many do, but it is ultimate.

Aircraft Spruce should have all the supplies you need including structural screws or rivets.

Steps

The new steps are reinforced. I recommend buying both and replacing. The other side may have the same problem. As mentioned, alodine is a good trestment. Find a local builder with some Alodine and some P69G2.