Aluminum and Stainless Steel

[LoFi2013]

Im Gathering parts and materials to do a large system upgrade and my question is distribution blocks.

I was watching the videos and Steve Meade said in the video for the chevelle always use Stainless fasteners on aluminum distribution blocks. I have a small (really small) background in machining and metals and im only going with what i was taught and what i've read over the past few days because it did not sit right but. From what I have learned these metals when combined tend to gall and the metals tend to corrode and cause failure when combined. Now again i've never actually used the two togeather and saw this happen myself.

my question is am i wrong in what i've learned because i have some very nice Aluminum Block i can use and no copper.

Im sure he would not use it in his own truck or others installs if it was a problem, and i trust someone in the business to know what they are doing i just want to know what im missing or why.

[ham4864]

Screws Compatible With Aluminum

make sure you choose a screw that's compatible with aluminum.

Aluminum is perfect for many applications that require a strong, lightweight metal. Aluminum has the greatest ratio of strength to weight of any of the metals. There are a number of types of screws that can be used with aluminum. The most common problem with using any type of screw in aluminum is corrosion where the screw meets the aluminum. There are ways to prevent this corrosion to assure that the screws stay in place and look good for many years.

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1. Types of Screws

   • Aluminum screws can be used with aluminum applications. Stainless steel is the most common screw to use with aluminum. Galvanized screws and aluminum bronze also work well in certain environments. Aluminum bronze is composed of aluminum mixed with other metals, such as iron, nickel, manganese and silicon. Aluminum bronze is commonly used in highly corrosive environments, such as in marine applications. Aluminum bronze usually contains between 5 percent and 12 percent aluminum in the blend. Titanium screws are also compatible with aluminum applications. Screws made from zinc and zinc mixtures will work with some lightweight aluminum applications that are not under high-stress conditions.

   Corrosion

   • Corrosion where screws meet the aluminum can be caused by moisture, corrosive liquids, heat and friction. Applications that are exposed to salt water are particularly vulnerable to corrosion. The stress caused by friction can loosen screws, allowing moisture to penetrate the connection and lead to corrosion. Structures that remain immobile, such as aluminum roofs, experience less stress that leads to corrosion than applications with moving parts. Corrosion can also be caused by a reaction between different types of metals, such as aluminum and steel or iron.

   Preventing Corrosion

   • To help prevent corrosion between a screw and aluminum, drill the proper size hole before inserting the screw. Pre-drilling the hole will prevent the protective oxide from being stripped from the aluminum and the threads of the screw --- this helps prevent corrosion. In applications where it is not necessary to countersink the screws, a washer made of nylon or other synthetic material can help prevent the friction that leads to corrosion. Sealants are available commercially that will help protect the surface between the screw and aluminum from the friction and moisture that leads to corrosion. Teflon or silicon can be used as insulators to prevent corrosion between different types of screws and aluminum. Even if you are using protective sealants or washers, you will still need to pre-drill holes before inserting the screw into the aluminum.

   Best Options

   • Depending on the type of project and the conditions to which the screws will be regularly exposed, stainless steel, aluminum, aluminum bronze and titanium screws are the best options for screws that are compatible with aluminum.