Surface Finishing of Steel and Aluminum
Tuesday, November 3, 2020
What are the two most commonly used metals in the automotive industry? Steel and aluminum.
Manufacturers use steel because it is the strongest, most affordable material out there for the application and can be engineered in a lot of different ways to meet the needs of crash safety and the performance of the vehicle. Aluminum is lighter and is as strong or stronger than steel.
However, both aluminum and steel parts often require some level of surface improvement prior to being used. Surface finishing, or polishing, is essential because it ensures the metal parts are adequately prepared for their intended application. By eliminating imperfections found on the surface of the parts, corrosion is minimized, coating materials are able to adhere properly, sharp edges/burrs are removed as well as improving the overall appearance of the part.
Each material has its own unique surface roughness. Processing of the part can also affect this surface roughness, as can additional processes performed on the part, such as welding, heat treading, etc. These factors are all taken into account to determine the optimal process to prepare the metal parts for its final stages, whether that is coating, polishing, texturing or assembly.
Today, let’s focus on coating.
Each type of coating dictates its own surface requirements. Coatings such as nylon or powder can “break” on a sharp edge; where as a coating such as plastisol can assist in covering up sharp edges. Regardless of the coating, metal surfaces must be clean to be coated. Any oils, grease or corrosion will impede the adhesion of the coating to the metal.
To remove contaminates, oil or grease from the surface, washing is often the solution. Depending on the geometry of the part and the requirements, there are many options, including hang washing, conveyor washing, barrel washing and ultrasonic cleaning. Each has its merits, and by using specialty compounds, most to all contaminates, oil, grease and rust can be removed using one of these processes.
Edge Removal/Internal cleaning
If there is an edge or burr that needs to be removed, or an internal area that a spray wash will not reach, deburring is an option. Tumble deburring, centrifugal deburring or vibratory deburring uses part on part or media and compounds to remove burrs and edges, other imperfections as well as cleaning off any contaminates. Deburring can also increase the lifespan of a part and increase its overall look.
Removing heat treat or casting scale is the first step when preparing parts for surface coating. Descaling can be accomplished through tumble deburring, vibratory deburring and blasting. The best process is again determined by the configuration of the part, the descaling required, and the base material. Laser cut metals experience heat scale on the edges, and powder coating will not adhere to these edges until the part is descaled.
Texturing the metal gives the coating more surface to adhere to. Blasting is a very common process to achieve this. The texture can be minute or quite pronounced.
Once the proper surface roughness is achieved, the coating can be applied. Whether the coating is powder, nylon, plastisol, e-coat, chrome plating, or any other common coating, a metal part will need to be prepped before coating. Latem industries offers every solution mentioned in this article to assist in preparing your metal parts for coating.
For any questions please contact us.
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