Re: Remplacement de vis

Avec enthousiasme, le 30 avril 2022 à 07:04, Geo écrivit :

De bilou, le 30/04/2022 :
>

Le 29/04/2022 à 08:04, jdd a écrit :

et non, une vis en inox va bouffer l'alu...

J'ai vu de rares cas d'alu bouffé par des vis ordinaires.
Sur des antennes en milieu marin.
Je ne suis pas sur du tout que l'inox soit pire.

>
C'est une question de cohabitation de l'alu et de l'inox en milieu
humide.
C'est de l'électrochimie.

J’ai trouvé un beau tableau sur ce sujet. Et si je le comprends bien,
moins l’écart est important moins il y aura de galvanisation. Cela
voudrais dire que l’or est très mauvais pour l’acier ! Je n’y comprends
donc rien.

Pour le texte et le tableau :
https://en.wikipedia.org/wiki/Galvanic_corrosion#Anodic_index

Pour le texte V.F. :

Une version compressée du lien :)
https://tinyurl.com/4k88etjz


La V.O. :
https://translate.google.fr/?sl=en&tl=fr&text=Anodic%20index%5Bedit%5D%0A%0ASacrificial%20anode%20to%20protect%20a%20boat%0AThe%20compatibility%20of%20two%20different%20metals%20may%20be%20predicted%20by%20consideration%20of%20their%20anodic%20index.%20This%20parameter%20is%20a%20measure%20of%20the%20electrochemical%20voltage%20that%20will%20be%20developed%20between%20the%20metal%20and%20gold.%20To%20find%20the%20relative%20voltage%20of%20a%20pair%20of%20metals%20it%20is%20only%20required%20to%20subtract%20their%20anodic%20indices.%5B17%5D%0A%0ATo%20reduce%20galvanic%20corrosion%20for%20metals%20stored%20in%20normal%20environments%20such%20as%20storage%20in%20warehouses%20or%20non-temperature%20and%20humidity%20controlled%20environments%2C%20there%20should%20not%20be%20more%20than%200.25%20V%20difference%20in%20the%20anodic%20index%20of%20the%20two%20metals%20in%20contact.%20For%20controlled%20environments%20in%20which%20temperature%20and%20humidity%20are%20controlled%2C%200.50%20V%20can%20be%20tolerated.%20For%20harsh%20environments%20such%20as%20outdoors%2C%20high%20humidity%2C%20and%20salty%20environments%2C%20there%20should%20be%20not%20more%20than%200.15%20V%20difference%20in%20the%20anodic%20index.%20For%20example%3A%20gold%20and%20silver%20have%20a%20difference%20of%200.15%20V%2C%20therefore%20the%20two%20metals%20will%20not%20experience%20significant%20corrosion%20even%20in%20a%20harsh%20environment.%5B18%5D%5Bpage%20needed%5D%0A%0AWhen%20design%20considerations%20require%20that%20dissimilar%20metals%20come%20in%20contact%2C%20the%20difference%20in%20anodic%20index%20is%20often%20managed%20by%20finishes%20and%20plating.%20The%20finishing%20and%20plating%20selected%20allow%20the%20dissimilar%20materials%20to%20be%20in%20contact%2C%20while%20protecting%20the%20more%20base%20materials%20from%20corrosion%20by%20the%20more%20noble.%5B18%5D%5Bpage%20needed%5D%20It%20will%20always%20be%20the%20metal%20with%20the%20most%20negative%20anodic%20index%20which%20will%20ultimately%20suffer%20from%20corrosion%20when%20galvanic%20incompatibility%20is%20in%20play.%20This%20is%20why%20sterling%20silver%20and%20stainless%20steel%20tableware%20should%20never%20be%20placed%20together%20in%20a%20dishwasher%20at%20the%20same%20time%2C%20as%20the%20steel%20items%20will%20likely%20experience%20corrosion%20by%20the%20end%20of%20the%20cycle%20(soap%20and%20water%20having%20served%20as%20the%20chemical%20electrolyte%2C%20and%20heat%20having%20accelerated%20the%20process).%0A&op=translate



P.S. J’ai mis fr.sci.chimie en copie.

--
Benoît
En essayant continuellement on finit par réussir.
Donc, plus ça rate, plus on a des chances que ça marche.
(Jacques Rouxel)