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From: =?UTF-8?B?IkJlbm/DrnQgTC4i?= <benoit@leraillez.com.invalid>
Newsgroups: fr.rec.bricolage,fr.sci.chimie
Subject: Re: Remplacement de vis
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Date: Sat, 30 Apr 2022 11:37:18 -0000 (UTC)
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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)