Читать книгу Media Blasting & Metal Preparation - Matt Joseph - Страница 9

INTRODUCTION

Recently, Ford announced that starting with the 2015 model year, all F-150 regular-duty trucks would come with aluminum bodies. The F-150 is the bestselling nameplate in the United States, and this is, by far, the most ambitious venture into volume aluminum motor vehicle production in the history of the automobile. After the first dust from that announcement settled, a storm of comment ensued about repairing the large number of aluminum bodied vehicles that would soon be hitting the streets and roads.

The difficulty and cost of repairs to those bodies soon became an issue in projecting the ultimate success of Ford’s F-150 aluminum alloy gamble. Major costs included training, facilities, and equipment to repair aluminum bodies. Professionals and the interested public quickly learned (if they didn’t already know) the necessity of clean metal in these repairs. Aluminum and steel body work in dealership and independent shops require completely different tool sets. Of course, this applies to spot and MIG welders, but it also applies to common items, such as the hammers and dollies, that touch the surfaces of aluminum and steel body panels and structures.

You cannot cross-contaminate aluminum or steel with tools used on the other metal. If you do hit aluminum with a steel or iron hammer or dolly, or with an aluminum hammer or dolly that has previously been used on a steel panel, you have the basis for electrolytic corrosion problems buried under the finish that you build over the metal. The same sequence applies to tools used on aluminum panels, and later used on steel panels. Tools used on steel continue to be made from iron and steel, but tools used on aluminum should be made from aluminum alloys.

It gets worse.

You should not weld steel or aluminum alloy in the same area in which you weld the other metal. If you do, airborne contamination from welding and shaping one metal may contaminate the surface of the other. You need separate facilities for the two metals, or, at the very least, you need to separate welding and grinding work on the two metals with pretty sound partitions and curtains. You also need to provide separate air extraction and makeup units. It is possible that you might be able to violate these rules in very low volume work, but as your workflow increases the risks become greater.

Behold the lowly, but endlessly useful, scraper. The one in front is a World War II surplus version. It was the first tool I owned, personally. It remains on my tool cart, more than 60 years after I first used it. The scraper in back is a later, more common version of this tool.

This example should give readers some sense of how important and how persistent the need for clean metal can be.

I entered automotive endeavors through the portal of restoration in my father’s shop in the mid-1950s. As you might expect, my first jobs involved cleaning things, mostly metal things. At age 11, I didn’t exactly have the knowledge, skill, dexterity, or strength to bolt down a cylinder head. Because nobody else in the shop wanted to clean parts, I was the natural and successful candidate for the job.

At first I was thrilled to be working in the shop at all. Soon, I wished that I could do the more complicated and glamorous stuff that the adults were doing, and eventually I did. However, my apprenticeship as chief cleaner and polisher lasted several years. At the time it seemed like several lifetimes.

I never disliked cleaning stamped steel parts in Stoddard solvent until my unprotected fingers tingled, sanding panels with “white gas” lubricant, or scraping and brushing the paint and rust off castings without any skin, lung, or eye protection. In fact, I kind of liked that work and always tried to perform it better and more efficiently each time it was assigned. It sure beat playing hopscotch with the other kids.

I quickly learned that different cleaning jobs required differing approaches. I learned what worked best in particular situations and how to transfer and apply that knowledge to other cleaning jobs. In return for my efforts I received what you might expect a preteenager to get in this situation, pats on my little head. I also got the great satisfaction of believing that I was beginning to know what I was doing.

From the ground floor, I came to see the cleaning racket as basic; in fact, so basic that its foundational importance was often overlooked by the older folks in the shop.

Over the years I gained considerable knowledge of and expertise in automotive cleaning work. I learned what worked well, what worked better than well, and what didn’t work well, or at all. Some of this was the result of instruction, some came from my own primitive research into what worked best, and a lot of it came from good old trial and error.

Later, when I had my own shop, I continued to seek knowledge about how best to clean things in terms of efficiency and the quality of my results.

I was fascinated by abrasive blasting and experimented with all kinds of equipment configurations and blasting media. I learned which media types and sizes worked best for specific purposes and how best to apply them. I also worked with various cleaning and polishing wheels and compounds. Again, I sought efficiency and quality in applying these processes.

Tumbling and vibratory cleaning processes, among several others, interested me, and I studied them for use in both industrial and custom work settings.

Visiting other shops, I often saw cleaning jobs relegated to very low status, with results that were sometimes harmful to the welfare of the projects that they supported.

Tools such as the large and small needle scalers (bottom) and the pneumatic scraper (top) are recent versions of once-exotic industrial tools. Their prices have come down enough by now to make them practical, affordable, and very useful cleaning devices.

New kinds of surface-cleaning wheels now supplement traditional sanding disks and wire wheel and cup brushes. The flap wheel (top) and the poly wheel (bottom) remove all kinds of rust and paint quickly and almost completely. Mounted on inexpensive, small angle grinders, they are reasonably economical to use.

At some point, I realized that I had gained the necessary knowledge to write a series of articles on automotive cleaning processes. As I thought about it, I decided that a book was a better format for this material because it would present it in a single place, avoiding the fragmentation of knowledge that I had encountered in learning the cleaning crafts myself.

When I presented my idea to Bob Wilson, the editorial director at CarTech, he quickly grasped its possibilities. I think that he may have once had a brush and can of solvent in-hand, likely more than once. We both saw the potential for a book that could inform and improve practices in a very basic part of working on cars, and, by so doing, improve the quality and durability of the work done on cars, not to mention the satisfaction of those performing the cleaning arts.

All of this had the potential to improve the efficiency and results in cleaning work. It also held the possibility of helping people who work with metal avoid some obvious but painful disasters.

In my own experience the one that comes most vividly to mind is paint failure caused by cleaning breaches or mistakes. Have you ever seen paint lifting off the area just above the roof drip rails on 1930s through 1950s restored cars? It is still pretty common. The cause is often paint remover and dip stripping chemicals that were incompletely removed from or neutralized at the seams where the drip rails attach to the roof. Another cause is failure to fully neutralize residues from the soldering fluxes used to attach those drip rails to their roofs. These errors can be avoided if you have a good working knowledge of what clean metal is and how to achieve it.

With all of the attention paid to advanced cleaning processes, including abrasive blasting, dip stripping, and industrial vibratory cleaning, you might conclude that this book may be talking about processes and equipment that are out of your price class. Some of it probably is. But a lot of what you find here is quietly revolutionary, very useful, and available at affordable prices.

Recent arrivals to the cleaning arsenal, such as poly and flap wheels that mount on small angle grinders and small, inexpensive pneumatic scrapers and needle scalers, can make a huge difference in your cleaning practices and results.

I hope that you find the material that is presented here useful. That was my intent.