From djozz:
How to add brass foil on the contacts
Q:
You can also get gold contacts.
https://www.aliexpress.com/item/33040243320.html
pure 24K is probably too soft.
plated Contacts should work better
or this: Gold plated copper
a quick google says, that is not correct,
lead tarnishes to a dull gray color
Tin tarnishes black
When I clean threads on a lamp it is always dark grey smudged.
There is no solder, lead or tin, involved in your case. Itâs just aluminum.
Nice find but I already have some thin nickel plated brass sticks.
my question was about the marks on positive driver pad caused by battery pole
I wanted fix it with a small solder blow from an alloy that does not form oxide and more hard than SN/PB.
Sounds like you want precious metals 
Trying to order from Sofirn but they ask for a lot. Canât just use PayPal. Just gave up.
you could sweat solder a small piece of sheet silver on there instead, it`s a better material than gold (or anything else) even it`s oxide conducts as well! it`s also a soft metal. I replace all sorts of flashlight parts with pure silver, it`s worth getting some in (for everyone into repair and modding).
Thx for suggestion 
Will try Ag sheet if I find it
Yea by the time they charge shipping at Sofirn same price. I was thinking folks were getting the c01 for $4
yes, but you have to buy 6 to get the free shippingâŠ
And how many of the co1s?
Tried 4 and got free shipping. Very confusing sight but hopefully smooth sailing from here.
Yeah if you notice up at the top of the Sofirn page, it says free shipping on orders over $21.
Not a bad dealâŠ.
Canât find that notice but thatâs what I needed to know.
Itâs in the blue band at the top of the Sofirn page.
Looked again nope but now I know.
Fo run stock Led at ~40 mA max.
Jumper with solder blow the 220 resistor without remove it
or I have to change resistor with lower value like 10Ω ?