Chromic Acid Anodize
Type I or chromic acid anodizing is used primarily by our aerospace customers in precision applications, as it is the thinnest form of anodizing and does not change a part's dimensions. The resulting color from chromic acid anodizing will vary from light gray to dark gray depending on the alloy. Type 1 is not as readily dyed as sulfuric anodize.
Sulfuric Acid Anodize - Type II
Type II aluminum anodizing is performed using a sulfuric acid bath to create the anodic aluminum oxide surface. This method is conventional anodizing. Type II anodizing is very versatile and provides an ideal surface for dye application. The resulting color will vary with alloy composition. Aluminum with low alloying elements will show practically no color change. This means Type II can be dyed practically any color or shade (black, blue, red, gold, orange, green etc.)
Sulfuric Acid Anodize - Type III
Type III sulfuric acid anodizing is commonly referred to as hardcoat anodizing as it is used to protect aluminum parts in harsh wear applications. Hardcoat anodizing creates a denser anodized layer that may reach up to 0.002" in thickness. Type III is dyed easiest of all because of the deep pores created. The hardcoat process darkens and alters the base metal enough so that the color is dramatically different than Type II, i.e. red dye on Type II is fire engine red while on Type III it is dark burgundy.
With electropolishing, the metal piece is fitted with two electrodes. One serves as the anode and the other serves as the cathode - they are connected to a DC power supply. The piece is then immersed into a bath of a specially formulated, temperature-controlled electrolytic solution. The the power supply produces an electrical current that passes from the anode to the cathode, resulting in the oxidation of the metal surface and the removal of surface impurities and irregularities.
Benefits of Electropolishing :
- Bright finish - Perhaps the most noticeable benefit of electropolishing is that it provides an immediate brightening of a metal finish. By eliminating or minimizing stains, heat discoloration and minor scratches, electropolishing can bring out the metal’s natural shine, which enhances the appearance of the piece.
- Increased corrosion protection - By removing surface imperfections, electropolishing can increase the piece’s resistance to corrosion. Its because the elimination of imperfections can prevent the moisture that leads to corrosion from accumulation. Electropolished pieces experience greater corrosion resistance than raw parts.
- Ultracleaning - Electropolishing offers remarkable ultracleaning capabilities through the removal of rust, imbedded scale and other foreign debris. This can be accomplished without stressing the piece or negatively impacting surface hardness and integrity.
- Improving micro finish - Electropolishing can effectively remove the microscopic peaks resulting from processes such as welding, forming and stamping. The reduction of microfinish values and accompanying increases in surface smoothness can be extremely beneficial in the production of valves and gears.
- Edge break removal - The ability of electropolishing to remove surface metal from a part makes it extremely effective in the elimination of edge breaks. That’s why electropolishing is often preferable to vibratory finishing or tumbling for use on delicate parts.
- Surface preparation - Because electropolishing creates a smooth, clean surface that promotes adhesion, it is used to prepare surfaces for processes such as coating, plating, welding and anodizing.