Thickened acid microemulsion composition

A thickened, shear thinning acidic microemulsion composition which comprises approximately by weight:

• (a) 1 to 6 percent of an anionic surfactant;
• (b) 1 to 6 percent of a nonionic surfactant;
• (c) 0 to 0.7 percent of a preservative;
• (d) 0.1 to 0.7 percent of a xanthan gum thickener having a molecular weight of about 1,000,000 to 10,000,000;
• (e) 0 to 0.3 percent of an alkali metal hydroxide;
• (f) 0.05 to 1.0 percent of phosphoric acid;
• (g) 0.01 to 0.5 percent of an amino alkylene phosphonic acid;
• (h) 2 to 10 percent of an acid mixture of succinic acid, glutaric acid and adipic acid in a ratio of about 1:1:1;
• and
• (i) the balance being water, wherein the composition has a pH of about 1 to about 4 and a Brookfield viscosity of about 200 to 1,000 cps at R.T. using a #2 spindle at 50 rpms.